Page 34 – Sparky's Answers

1988 Cadillac Brougham, Windshield Wipers Do Not Work

This 1988 Cadillac Brougham came in with the complaint that the windshield wipers do not work. I have not worked on one of these in quite a while but I do remember the common problem with the rear wheel drive Cadillac wiper switches. I checked the feel of the switch and sure enough, it “felt” a little loose inside. The clicks were less distinct than they should have been. This is a pretty simple repair if you can just figure out how to get in there to the switch. The first thing to do is to remove the knob from the left vent control switch.

An 1/8″ allen wrench is needed to loosen the set screw.

Next remove the three phillips headed screws along the lower edge of the dash trim panel.

Then remove the screw at either side of the instrument cluster.

Then you have to look closely at the upper right corner of the left driver’s side vent. There is a single phillips headed screw in that corner. Loosen that screw. It may or may not come all of the way out of the vent opening. If it does not want to come out just try to make sure that it is wedged in such a way that it will stay in place within the assembly.

Turn the ignition on. Drop the shift lever all of the way down. Tilt the steering column fully down as well. This will allow enough room to remove the dash trim plate. In some year models the lower dash cover that fills the gap below the steering column will need to be removed as well as the crescent shaped cover just above the steering column. I cannot remember which years this applies to. After all they stopped making these cars about twenty years ago.

Now remove the screws that hold the switch in place and carefully unplug the harness connector. I state carefully and you will see why in the coming pictures.

This is the wiper switch removed.

This is the problem with the wiper switch. The back cover has separated. I know that I can fix this switch but why bother? I have installed quite a few of these switches over the years and as I remember the switch only lists for about $30 US. Well that is not the case today. The supply is nearly gone and the cheapest one I could find was about $170 US.

Time to break out skills from days gone by. I took a soldering iron and while holding the switch pieces firmly together, I melted the plastic pieces to form a bond.

That by itself is enough to hold the switch together if the driver is informed, to not push in firmly on the switch handle. However since plastic weld epoxy is readily available, I decided to use some to reinforce this repair. Another one fixed and cheap!

2003 GMC Yukon Bower Erratic / Not Working

This 2003 GMC Yukon came in with the complaint that the blower was doing weird things. The blower sometimes would not turn off when the ignition was turned off. Also sometimes the blower worked and sometimes it did not. Withe the local temperature expected to top off at over 100 degrees F and the the index expected to reach 120 degrees F, the customer said it had to be fixed. I agree.

The first step is to remove two of the three 7 mm screws (center and right hand), that hold the hush panel on under the passenger side of the dash.

With the hush panel dropped down, it is a quick test of the wiring, click here to see that information. The two most common failure symptoms with this part are an inoperative blower motor or a blower motor that will not turn off even with the key off. For testing information please see these repair articles. 2003 Chevrolet Silverado Blower , 2004 Chevrolet Silverado Blower Will Not Turn Off. and 2005 Chevrolet Tahoe Blower Not Working (video).

Using a screw driver or similar device, depress the locking tab and disconnect the wiring to the blower motor.

Remove the two screws holding the blower speed controller in place.

Push in the locking tab and disconnect the three wire connector from the blower speed controller.

Install the foam spacer on the hole marked 800 on the end of the unit that has four holes.

Mount the blower speed controller using the supplied screws. You will be using the mounting holes marked 800 on the new unit. Note the foam spacer under the left mount in the picture below.

Install the new wiring into the blower speed controller.

Connect the harness to the blower motor.

Cut and splice one wire at a time. Stagger the joints so that the wiring harness will be neat and trouble free.

Remove the BLWR fuse in the under hood fuse box before cutting the red wire. You might be tempted to disconnect the battery instead, but I do not recommend it. The act of disconnecting the battery does two things that can be detrimental: 1) Loses learned memory, which could result in a poor idle condition, and 2) Starts the recalibration procedure for the HVAC actuators, which may result in stuck HVAC doors and more expense.

Wrap tape back around the harness and put the hush panel back into place. Keep in mind that the old part number 15-80567 is no longer available and it has been replaced by this new kit. If you need this blower speed controller kit, please click here.

Another one done.

I decided to do some updated testing due to the design change by GM. There is still a constant 12 volt signal on the Red wire and constant ground on the Black wire.

Things have changed on the purple wire though with the new blower speed controller installation. One can test from the red wire to the purple wire or from the black wire to the purple wire with your voltmeter. GM recommend’s checking from the red to the purple but I prefer checking from the black to the purple. My reasoning is that it educates us that the blower speed controller has a nominal 12 volt output on the purple wire that the a/c control head signal brings down by applying a pulsed ground signal to. The chart starts at the highest blower position and descends one notch at a time to the lowest blower setting.

Red wire Purple wire Black wire Scan Tool Duty Cycle
8.57 volts Highest Speed 4.65 volts 78%
6.65 volts High -1 6.75 volts 59%
5.10 volts High -2 8.50 volts 43%
4.08 volts High -3 9.65 volts 33%
3.27 volts High -4 10.52 volts 25%
2.71 volts High -5 11.15 volts 20%
1.98 volts High -6 11.95 volts 13%
1.32 volts Lowest Speed 12.64 volts 6%

Keep in mind that the voltage is due to the duty cycle of a switched ground from the a/c control head. In bench testing I have confirmed that applying a constant ground to the purple wire will only yield a single pulse from the blower motor. Repeating the applied ground multiple times in a short period will allow the motor to run. I do not know if this added info will help anyone or not but I thought it was at least interesting from a technical perspective.

There is a new development in this repair. It seems that General Motors has added or changed a circuit in the new module that reduces what they refer to as “Thermal Events”. In doing so the new module does not always play well with aged blower motors. What we wind up with is this. The blower motor will not work on an engine restart unless the a/c controls were switched off before the ignition was cycled off and back on after the engine is running again. The two immediate ways to address this issue is to learn to remember to cycle the switches in the above manner or replace the aged blower motor with a new one. I suspect there may be a software update somewhere down the road but that will require dealer level programming abilities. Since the replacement part is only available from GM or through an ACDelco distributor we are all being subjected to this problem.

There was not a software update but another part is now being supplied and so far with no unexpected issues. Click here for the new product link.

The latest design ACDelco part is distinguished by being a light gray in color.

2006 Lincoln Zephyr Low Beam Headlight Does Not Work

This 2006 Lincoln Zephyr came in with the complaint that the right low beam headlight does not work. The owner had already installed a new Xenon or HID bulb assembly. If you merely want to change the bulb there is an access panel in the inner wheel well as shown in the following picture. Since the customer had already advised me that they had installed a new bulb but that did not fix the problem, I did a quick test of the wiring and found battery voltage on the yellow/gray wire (terminal 6) with the low beams turned on. I also checked and found that the ground signal was present on the black/gray wire (terminal 1).

I had to go much deeper to get the light assembly out. This involves removing the entire front facia. I started by removing the retaining pins at both wheel wells.

I then removed the multitude of screws on the under side of the car that secures it to the body.

With everything loosened up, I found that there was one phillips headed screw at the outside edge of the facia assembly. I had to pull the inner fender panel back and use a screwdriver to remove each screw. One each side. I forgot to take pictures but there are several phillips headed screws that have to be removed along the upper edge of the grill as well.

I though I had everything taken care of until I found that the facia would not come off. There was still something holding each side. I carefully inspected the situation and found locking clips at the body line. I worked with it and finally released the clips.

The panel needs to be flexed enough to allow the inner locking hooks to come down far enough for them to release from the locking tabs. In the next picture I am pointing to the hook that has to be forced down.

This is a picture of the locking tab that has to be forced up while the hook is being forced down.

The whole front facia off the car and on the floor.

The next picture shows the ballast or transformer module for the HID lighting system. I still needed to remove the light assembly to gain full access to the ballast/transformer.

There are four bolts and one push pin holding the light assembly in place. Two of the bolts are on the upper edge and there is a push pin at the top outer edge near the fender.

One bolt at the outer lower corner.

One at the inner lower corner.

The light assembly is out and I can now get the the ballast/transformer module wiring with ease.

Four screws and the unit comes off.

I checked the wiring terminal locations on the vehicle harness connector.

I then matched the harness terminals to the housing terminals. Performed a continuity test from the housing terminals to the terminals at the ballast/transformer plug. I also performed a test from the ballast/transformer terminals to the terminals at the light bulb assembly. All continuity tests were good so the diagnosis is a faulty ballast/transformer module. I used probes with very fine wire tips to be able to touch the terminals without damaging anything. Too large of a probe and or too much force and the terminals will be damaged. The wiring inside the light assembly cannot be repaired or replaced. You must purchase a complete light assembly. DO NOT UNDER ANY CIRCUMSTANCES TEST FOR VOLTAGE AT THE BULB WIRING WITH THE VEHICLE HARNESS OR ANY POWER SOURCE CONNECTED TO THE LIGHT ASSEMBLY! YOU WILL/MAY BE PHYSICALLY HARMED OR KILLED!

A new ballast/transformer module and the low beam HID light is working again. As a side note I did take the module from the driver’s side light assembly and installed it into the passenger side to confirm that the new bulb and the old bulb were both good. The customer wanted the old bulb installed. He purchased a new module from the local dealership. I reassembled the car and he put the new bulb up for future use.

2004 Chevrolet Tahoe, Rear Blower Will Not Turn Off.

This 2004 Chevrolet Tahoe came in with the complaint that the rear blower would not turn off and the battery went dead as a result. This Tahoe has manual a/c controls. The first thing that I did since the vehicle had to be jumped off to get it to my shop was to turn the engine off and install a battery charger. While the battery was charging, I started checking things out. I located the RR HVAC fuse in the underhood fuse box and pulled it out. I show the fuse location at the end of this post. The fan turned off and I went to print out a wiring diagram of the system. When I came back to the Tahoe with the wiring diagram, meters, and basic 1/4″ tools, I installed the fuse and the system was now working correctly…well, almost. I noticed that there was no high speed unless the switch was rocked back and forth. Almost like there was a “sweet spot”.

I checked that condition and it was the same at the front or rear switch panels. Not likely that both switches failed in the same way at the same time.

I continued to the rear of the Tahoe to find the blower resistor assembly. The diagram showed that it contained three relays and a resistor assembly. It also showed its location behind the right rear interior panel.

To remove that panel, the related trim panels have to be taken off first. The floor trim panel lifts off with a little bit of force.

Then the ceiling trim panel comes off in the same manner.

A close up of one of the retaining clips.

Then the right rear pillar panel. I started at the top and worked my way down.

This Tahoe had a speaker that had to be disconnected.

Now the cargo net retainer. It unscrews but I had to wrap it with a rag and use a pair of smooth jaw pliers to break it loose.

Then the push pin retainer.

I could then pull the panel back far enough to work.

Testing goes as follows:

Four wire harness connector:

Terminal “A” Black wire is a constant ground.

Terminal “B” Orange wire has a constant 12 volts power supply from the RR HVAC fuse in the underhood fuse box.

Terminal “C” Brown wire has a 12 volts switched ignition and is an output from the resistor. Meaning that it will only have power on it with the key on and the resistor harnesses connected. It’s power source is terminal “D” of this same connector and it sends ignition voltage to the rear mode and temperature door actuators.

Terminal “D” Brown wire* has 12 volts switched ignition supplied through the IGN 3 fuse in the left instrument panel fuse box.

*By the wiring diagram the wire color should be brown but in the vehicle it was brown with a blue dot.

At the three wire connector:
Terminal “A” Dark Blue wire is switched ground for low speed.
Terminal “B” Red wire is switched ground for medium speed.
Terminal “C” White wire is switched ground for high speed.

Testing for a switched ground should be done with the harness disconnected from the resistor assembly. If you were to test with the harness connected to the resistor and the key on you would find power on all three wires with the blower switches placed in the off position. The power would be bleed through voltage through each relay coil. Near zero volts would be present on any one wire that was in the switched ground position.

All of the signals were correct so I installed a new resistor assembly. Two 7 mm screws held the resistor in place. I also did some checking and found that this resistor and repair procedure will apply to 2000, 2001 2002, 2003, 2004, 2005 & 2006 Chevrolet Tahoe and GMC Yukon. It also applies to 2002-2006 Cadillac Escalade. If you need one of these resistors please click here.

Now I will admit that testing is a bit awkward with the main cover panel in place but to fully remove the panel the right rear seat belt assembly has to be removed. The right rear floor trim panel has to be removed and the pillar panel also has to be removed.

In the picture below I point out the RR HVAC fuse located in the underhood fuse box.

The underhood fuse box legend.

1997 Pontiac Grand Am, Key Will Not Turn Off, Replacing a Faulty Shifter

This 1997 Pontiac Grand Am came in with the complaint that the ignition key will not turn all of the way off. As a result the battery would go dead. I showed how to temporarily overcome this problem in a previous post. Please click here to see that post.

Testing begins by checking the PRNDL fuse, 10 amp in the left dash fuse box. It should have power on it in all key positions except for Lock and Accessory. Next check the ERLS fuse, 20 amp in the underhood fuse box. It should have power on it in the Run and Crank positions. Assuming that both fuses were okay, the covers on the steering column now need to be removed.

The top half unsnaps and lifts off.

The lower half has a few screws that need to be removed.

I used a screwdriver to remove the tilt lever handle.

With the covers removed I located the two wire connector for the ignition lock solenoid. I used an angled pick to back probe the connector on the White wire.

I then touched my grounded test light to the pick. No power.

Time to access the shifter wiring. I did not get a picture of removing the shifter handle but it is very easy. On the front edge of the shifter handle you should be able to feel a slot in the material. Using the same pick I used to back probe, I slid the point of the pick into the slot and found the edge of the metal retaining clip. The clip is a piece of flat metal about an 1/8″ wide. It is bent into the shape of a “U”. For those of you with a rural background it looks like a fence staple.

Next, remove the liner from the cup holder and then remove the screw.

The same thing at the rear cup holder.

Open the storage compartment and there will be two more screws to remove.

Now, remove the center console assembly. This usually requires dropping the shifter into the lowest gear and lifting the parking brake handle. Once the console is part way up, you may have to reposition the shifter and park brake handles. You can now see the disconnected harness plug between the shifter and the park brake handle.

A closer view of the harness connector end.

The back view of the same connector. I located the Pink wire at terminal “F” of the connector and checked for power in all key positions except Lock and Accessory. Power was present. Next I jumped the Pink, terminal “F” wire, to the White, terminal”C” wire.

I reconnected my test light setup and power was now present on the White wire. The key will now turn off as designed.

To change the shifter out from this point you have to remove the mounting nuts/bolts.

Use a screwdriver to remove the shifter cable end.

Use a screwdriver to remove the locking clip from the cable mount. Looks like a staple made from flat stock.

Push in the locking tabs on the plastic cable mount to release the cable from the bracket.

Pull the cable assembly from the bracket and remove the shifter assembly from the car.

Reverse the procedure to install

1997 Pontiac Grand Am, Ignition Switch Will Not Turn Off, Key Cannot Be Removed

This 1997 Pontiac Grand Am came in with the complaint that the ignition switch will not turn all of the way off. This causes two other problems. The key cannot be removed from the ignition lock cylinder and the ignition stays on enough for the systems not to shut down fully. The battery will go dead as a result. This is an increasingly common problem on many GM cars. This repair is only about how to get the ignition, switched off fully, so that the key can be removed and the battery drain condition can be avoided.

Look at the underside of the steering column plastic housing. You should see a removable section as shown in the picture below.

Place the tip of a spare key or a flat blade screwdriver into the slot as shown below. Using the slot as a pivot point, gently push the key head or screwdriver handle towards the base of the steering column. You just need to flex the forward edge of the insert panel enough to clear the main plastic cover.

Now, slide the insert on the direction of the arrow to remove the insert from the housing cover.

With the access cover removed you now have enough room to use the ned of your finger to locate the steel button and push it in. With the button/pin pushed in you can now turn the ignition key all of the way off.

I removed the cover in order to give you a better view of the pin/button that needs to be pushed in to release the ignition switch and therefore the key.

Keep in mind that this is just a mechanical override to allow the key to be switched off fully. It is not a fix. I will do a post about diagnosing and replacing the faulty part soon. In this case it was a faulty floor shifter assembly. Click here to see that post.

2004 Chevrolet Silverado, Changing The Passenger Side Blend Door Actuator, B0424

This 2004 Chevrolet Silverado came in with a faulty passenger side blend door actuator. In the last post I got you to this point. If you have not yet read that post please click here. Now that the dash cover is off and you can see the actuator, but you still cannot get to it. More things need to come apart.

Remove the wiring hold down clips from the metal brackets as shown below.

Remove the 7 mm headed screws from the brackets on the passenger side.

Using a ratchet remove the two 10 mm headed screws from the front edges of the bracket on the passenger side.

Remove the 7mm screw from the driver’s side of the cross over bracket. Remove the bracket.

Now the “U” shaped bracket on the passenger side can be removed.

Remove the 7 mm screws on the driver’s side bracket. I also remove the two 10 mm bolts on the driver’s side bracket to make sure the dash will move around freely.

Disable the air bag or SRS system according to the manufacturers directions. Then remove the two upper 10 mm bolts from the air bag as shown in the next two pictures.

Then remove the two lower air bag screws.

Note that the air bag screws are shorter than the bracket screws. Do Not put the long bolts back in the airbag when reassembling.

< Pull the orange "positive assurance clip" from the yellow connector. Disconnect the connector and remove the airbag. Use the manufacturers recommendations for handling and storing the airbag.

Getting close but more still has to come out. The silver box shown below is the vehicle communication interface module. It may not be present on all vehicles as it is related to the Onstar System.

There are three 10 mm nuts that hold the module to the brackets. They are locking nuts so they have to be wrenched all of the way off.

Remove the two 10 mm nuts at the passenger end of the dash carrier. Do Not mix these nuts up with the ones removed from the VCIM brackets.

Now remove the 7 mm screw from the backside of the right passenger vent.

Remove the 7 mm screw from the position shown below.

Wiggle the corner of the dash out as shown below.

I used a screwdriver handle to keep the duct work lifted.

I also used a pry bar to lift the duct work slightly to give myself more room. The weight of the pry bar is enough to keep the duct work up but you may want someone to hold it for you. If someone hold it for you be sure they do not use the area in the center of the opening for a fulcrum. It will break the mounting panel where the nut is for the phillips headed screw that was removed much earlier.

The VCIM can now be wiggled up and the wires disconnected.

Remove the wiring harness retaining clip from the bracket as shown below.

Remove the wiring harness clip from the cross bar as shown in the two pictures below. Lift the harness slightly to gain more room to work.

Using a short 5.5 mm socket and ratchet, remove the two mounting screws. Disconnect the wiring from the actuator before removing the screws. makes it a little easier.

You will actually need to work through two openings and use both hands to make it easier.

A magnet on a stick works real well fro retrieving dropped screws and sockets.

You can finally remove the actuator from the dash.

Free at last.

The new and old actuators. The numbers match 52402588.
If you need to buy one of these actuators please click here.

If you do not have a Tech 2 or similar scan tool to diagnose these actuators, you can do voltmeter testing at these connectors. That is a whole other post though.

2004 Chevrolet Silverado, Dash Cover Removal

This 2004 Chevrolet Silverado came in with multiple hvac actuator faults. After diagnosing a faulty passenger side blend air door actuator with my Tech 2 scan tool it was time to remove the dash cover. Not a big deal but there are a lot of steps.

Lift the lower edge of the dash end caps and remove the covers.

There are two phillips headed screws. A short screw driver is needed to do this. Remember to do this on both sides of the dash.

Using a small screw driver or other similar device, gently pry the passenger side vents from the dash.

Work the vent out evenly. If it is cocked to one side or the other it will tend to jam.

There is a phillips headed screw under each vent on the passenger side.

Repeat the process on the other vent.

Now, look up into the upper edge of both vent holes. You will see a white push button. Depress the buttons. The buttons depress to the center of the handle assembly. The right side pushes to the left and the left side pushes to the right.

Pull the passenger handle from the dash. You can alternate from side to side until it is fully removed or you can have someone assist you.

Grasp the upper edge of the trim panel and pull out. Once the upper edge is released, work the panel up until it releases from the dash panel.

Rotate the panel over to expose the tweeter wiring, if present. Depress the locking tab and pull the connectors apart.

Grasp the upper edge of the dash face panel and pull it loose from the dash.

Work around the dash face until all of the clips are free. Tilt the steering wheel fully down. Turn the ignition on and drop the shifter handle all of the way down. Roll the upper edge of the dash face out towards you. The panel will have to be flexed above the center of the instrument cluster to release the face panel fully.

A better view of releasing the “A” pillar trim panel.

Remove the 7 mm headed screws around the edge of the dash cover panel.

Once all screws are removed, the dash cover will pull off of the dash carrier. It has to be pulled away from the windshield to release the forward clips. Then lifted slightly to clear the leading edge of the dash carrier.

Most trucks will have the ambient light sensor and possibly a sun load sensor mounted to the underside of the dash.

The ambient light sensor twists out like a light bulb. Be gentle with this part as it is fragile. If it has the second sensor, it has to be unplugged.

Support the dash cover evenly as you pull it from the vehicle.

Now , remove the two 7 mm screws that hold the right driver’s side vent register in place. Remove the vent register.

Remove the panel holding the passenger side airbag switch. The panel may be blank in some years. It pulls out and uses spring clips to hold it in place.

Now, if you look under the vent duct you will see the wiring for the passenger side blend air door actuator. Look closely and you should see the actuator itself.

This post is so long that I am breaking it up into multiple posts.

To see how to change the recirculation / fresh air door actuator please click here.

To see how to change the passenger side blend air door actuator from this point, please click here.

2003 Ford Expedition, No Run, No Fuel Pump Operation, Code P0231

This 2003 Ford Expedition came in with a no run condition. A quick check found no fuel pressure and a code P0231 (low voltage on fuel pump monitor circuit). I decided to go to the interior fuse box, where my wiring diagrams, stated the fuel pump relay and fuse are located. There are a couple of covers that have to be removed.

Pull the edge loose at the firewall end and pivot the cover back.

There is a black plastic cover that has to be pulled off of the actual fuse box.

Since my wiring diagrams stated the relay was located in the fuse box, but did not give a specific position, I looked in the owners manual for more info. No luck there. I did some reading and found that there are five internal, non serviceable relays inside the fuse block. My next test would involve locating the output circuit from the relay. The wiring diagrams stated that the fuel pump relay output wire was dark green/yellow and it was located in cavity 3 of connector C270K. I placed a jumper wire into the cavity to backprobe the circuit, no volts. Since my backprobe wire is part of a fused jumper wire, I connected battery voltage to the circuit and started the vehicle. This told me that the fuel pump, inertia switch and related wiring were all okay.

I checked fuse #34 with the key on and it had power and was good so that eliminated a faulty pcm relay and related wiring. The next step was to locate the light blue/orange wire in cavity #12 of the C270B connector. It is in the lower right hand corner of the twelve cavity connector just below the connector that I am backprobing in the picture above. When the ignition is turned on the reading was near zero volts and after a few seconds it went to battery voltage. This told me that the pcm was using a ground to energize the fuel pump relay coil. With all of this testing I knew without a doubt that the fuel pump relay that is part of the interior fuse box was faulty.

Disconnect the battery first before removing the fuse block. There is a battery feed cable that also has to be disconnected on the rear edge of the fuse box. It is located under a cover. I have pictures of that at the end of this post. There is only one bolt that holds this fuse block in place.

I unplugged all of the wiring. There are connectors on the top where testing was done and on the edge. Above and below the mounting bolt.

In the rear.

This connector has a slide mechanism. I have my finger in the pull handle for it.

The fuse block removed from the vehicle. You can see the battery terminal post on the lower left edge.

I carefully removed all fuses and relays from the fuse block and laid them out in the order removed.

I took the back cover off of the fuse block and started disassembling it.

Once I had it opened it was easy to see the damage. Slightly right of center.

The damage was even easier to see from the relay side of the board. I feel fairly confident that if this problem would have been caught soon enough, the solder joint could have been repaired or a new relay installed (if one could have been located).

The old fuse block on the left and the new one on the right.

I plugged everything back in and bolted the fuse block in place.

This is the end of the battery cable that I referred to earlier.

The cover for the battery stud on the fuse block.

I put all of the covers back on, cleared the codes and test drove the vehicle. This one is done.

This repair will generally apply to Ford and Lincoln full sized trucks and suv’s in the same years//body style. Check diagrams and component locators before jumping any circuits, as I did.

2003 Chevrolet Silverado, Changing the Mode Actuator, Code B0263

This 2003 Chevrolet Silverado came in with the air flow stuck on defrost. A simple diagnosis of a code B0263 found a faulty mode actuator. This repair applies to 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, and 2011 Chevrolet Avalanche, Silverado, Suburban and Tahoe. It also applies to Cadillac Escalade, GMC Sierra and Yukon for the same year models.

It is specific to all models WITH auto a/c controls.

Models with manual a/c controls, WITHOUT a factory floor mounted center console.Trucks that have manual a/c controls and WITH a factory floor mounted center console, use a slightly different actuator and procedure. On that model the gear/cog seperates from the actuator. Before removing that actuator use something to hold the gear/cog in place while the actuator is being removed. If it comes off, it will take some time to figure out where the gear/cog and the three levers go. I hope to do a post on that model soon.In the meantime, if you need to order this part for a full sized truck or suv, that has manual a/c controls and a factory floor mounted center console (RPO Code D07), that is not shown in this post, please click here.

Now onto this repair.The actuator is located under the driver’s side of the dash, above the gas pedal area, and on the end of the heater a/c case.

I know this will seem quite simplistic but the very first thing I do during this repair is, to push down the parking brake pedal. I cannot turn under the dash with it up.

Then either by hand or using the tool shown in the pictures, I pull the retaining pin out that holds the heater duct in place.

A better view of the retaining pin.

This is the view of the heater vent with the extension removed. The actuator is above the duct. Inn case you are wondering the piece in the duct is the duct temperature sensor.

A better view. I had to place the camera behind the brake pedal so the angle is slightly different from what you will see. There are two 5.5 mm headed screws that hold the actuator in place. The upper screw also holds the wiring harness retaining clip as well. I have pictures of that later. Try to set the old actuator to the same position as the new one before removing. To do this switch the ignition on and have someone depress the defroster button for you. While looking at the slot on the center shaft also have one hand on the ignition switch. Turn the ignition off just before the slot lines up with the appropriate hash mark. If this is not possible for you just set the controls to the split defrost and floor position. This will make it easier to slip the actuator out. Lift the edge of the actuator, that is closest to the firewall, away from the heater a/c case. It can take a good bit aof patience and manipulation to remove the old actuator. So take your time and don’t caveman it out.

This enables the large cog to come out from under the pin on the white lever gear. Remember which slot it was in, the inner one.

Now that the actuator is out of the way, you can see the two door levers. The small black one to the left is for the defroster door. The larger white one with the gear teeth attached is for the vent / floor door.

The old actuator on the left and the new one on the right.

Note the position of the actuator cog to the actuator motor. The actuators come prepositioned to allow for easier assembly. Do not connect the wiring to the actuator until the new actuator is installed. If you do for some reason, refer back to this picture to reindex the actuator to the correct position.
To purchase a new actuator please click here.

Slide the new actuator into place in the reverse order that you pulled it out. Once it is generally back in place make sure that the peg on the back side of the white gear lever is in the inner slot of the actuator cog. Then while holding it gently in place reach up to the top side of the cog and make sure that the defroster lever is in its slot under the cog. Now take your time and gently maneuver the actuator around until the actuator drops completely into place. The two door lever pins have to be lined up. The actuator has to be lined up with the two mounting bosses, the center rings on the actuator cog and the heater a/c case also have to be lined up. Remember patience and gentle maneuvering and it will drop that last little 1/4″ to 3/8″ to the mounting bosses. Do not force or use the screws to draw it down. You will likely break something or have a jammed actuator at the very least.

Remember when installing the mounting screws that the upper screw hold down the wiring harness retainer clip.

I used a 1/4″ palm ratchet and 5.5 mm deep well socket to remove and install the screws.

The new actuator installed.

This truck has auto a/c controls. The part and the basic repair are the same whether it has manual or auto controls. I have not done one on the newer body style truck but I would assume at this point it will be similar. This repair of course should be generally the same for 2003 through 2007 Classic series trucks and suvs.

Remember to preset the controls to the split defrost / floor position before removing the old actuator. If needed, use a small screwdriver or the edge of a quarter to rotate the actuator into the correct position. Once in place disconnect the wiring at the actuator. If you are manually assisting the actuator, you must do it withing the first minute or two of switching the ignition on. The system will try to adjust to the commanded position for a minute and then stops trying. At that point the motor will not be able to be assisted. The ignition will need to be turned off for at least ten seconds and then back on for another attempt.

To perform a recalibration of the newly installed actuator, I used a Tech 2 scan tool. If you do not have a scan tool you have two choices. Remove the fuse shown below for one minute or disconnect the battery for one minute. After the fuse is installed or the battery is reconnected, start the engine and let it run for at least one minute (I prefer the old time of 4 minutes). DO NOT TOUCH the a/c controls during this time. Turn the ignition off for at least ten seconds. Restart the engine and check the a/c operation.

The fuse location and name may be different for other vehicles. This of course is a 2003 Silverado.

Please look closely at the picture below so that you can identify where the two door levers are. I have had some people tell me that there is only one. The defroster lever has a pin sticking up that has to be aligned in a closed slot in the under side of the actuator cog. The white vent/floor gear lever has a pin on the underside that must drop into the inner open slot in the actuator cog. The gear teeth should self align when the actuator is moved.

I am building a test procedure for this actuator. Current testing is as follows.

At the mode actuator, with the ignition switched on, check for battery voltage on the brown wire.

Check for a 5 volt reference signal on the light blue/black wire.

The yellow wire should show ground as it is the reference low signal from the control head assembly.

The light green wire should have a variable 0-5 volt signal on it. This is the actuator position signal.

The tan wire is the command signal wire. There should be one of three voltages present as different modes are commanded.

5 volt signal is the command for counter clockwise rotation.

2.5 volt signal is the stop command.

0 volt command is for clockwise rotation.

I have found through bench testing an actuator that there is a nominal 2.5 volt output from the actuator on the tan wire. The control head therefore must apply a ground on the tan wire to reduce the voltage to zero to command clockwise rotation. It must also apply voltage to bring the reading to 5 volts in order to command counter clockwise rotation.

All voltages referred to above should be considered nominal volts. In testing, I found that a variation of .75 volts from the 2.5 volt stop command was enough to move the actuator.

When doing testing, if you find no variation on the tan wire, do not jump to the conclusion that the control head is faulty. The system will go into a “sleep mode” if a hard fault is found with an actuator. The system will determine this within a minute or two of turning the ignition on. You have to have your meter set up and ready to see the reading before you actually turn the key on. You may also have to clear hard fault codes before the system will even try to move the affected actuator. You can clear the codes with a scan tool, remove the HVAC memory fuse or disconnect the battery.

If any of the signals are missing, check the wiring at the right and left junction boxes at either end of the dash. Look for signs of corrosion, general looseness or fretting. Locations can vary from year to year and model to model. Please consult a wiring diagram.