2005 Cadillac Escalade, Driver’s Side Vents Blow Hot Air, A/C On

This 2005 Cadillac Escalade came in with the complaint that the driver’s side vents have switched to blowing only hot air with the a/c on. The passenger side air is cold.

The telltale B0408 code for a faulty driver’s side blend/ temperature door actuator. Granted most people do not have a dealer level scan tool to work with, but there are ways around that. I will discuss that later.

The repair begins with removing the passenger side lower dash hush panel. There are three screws that hold this panel in place and all three have to be removed to replace the actuator.

The first one is easy.

The second one will not accommodate a power driver so I had to switch to a ratchet.

The third one is a little difficult.  A standard ratchet will do the job but this little 1/4″ drive palm ratchet makes it easier for me.

Getting that third screw out is difficult but re installing it properly is near impossible. The hole is slotted and there is a recessed ring at the outer edge of the hole.

Okay the panel is now out of the way.

To do testing with a voltmeter at the harness connector you will need to test the following.

Check for ignition power on the brown wire. If power is not present check the HVAC 1 fuse in the left interior fuse box.

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

All of the following backprobe tests must be done with the harness connector plugged into the actuator. 

The yellow wire is a low reference circuit from the control head (ground, technically internal system not chassis).

The light blue wire is the position signal wire from the actuator to the control head. If the actuator will move when commanded the voltage will change up or down depending on the movement of the actuator (nominally between 0 and 5 volts).

The dark blue wire is the command circuit from the control head to the actuator. It will have basically three different voltages that are important:

.5 volts is a signal to increase the door position,
0 volts is a signal to decrease the door position
2.5 volts is a signal to hold/stall the door position.

So with that information turn the ignition on and touch the black lead of your voltmeter to the yellow wire. Touch the red lead of your meter to the brown wire and check for a reading of battery voltage.

Follow that up by having your black lead on the yellow wire as before and now place the red lead on the light blue/black wire. You should see a 5 volt reading on your meter.

These two tests are to confirm a valid low reference signal on the yellow wire, ignition voltage on the brown wire and a five volt reference signal on the light blue wire. If a nominal 12 volt and 5 volt reading are not found further testing will need to be done using a known good chassis ground.

Assuming the above tests went okay the next step would be to test the command circuit on the dark blue wire.

With your black lead still connected to low reference or a good chassis ground, touch the red lead to the dark blue wire and check for either 0, 2.5 or 5 volts depending on command. You will probably need an assistant to adjust the temperature control for the driver’s side.

If a hard code is stored the command signal may be locked. This would be evident if you are using a scan tool. If you are not you may need to clear the presumed codes by performing a system recalibration. A system recalibration involves removing and reconnecting the battery /memory circuit for the HVAC control head.  Recalibration Procedure.

Also if the HVAC control head does not receive the proper position feedback signal from the actuator withing two minutes of the ignition being turned on the command signal will be locked.

Testing can also be done at the junction block at the passenger end of the dash. It is not as accurate as testing at the actuator and the HVAC control head assembly but it is easier. It lacks accuracy because it is done at a midpoint  of the components. Link to junction block testing.

Assuming that testing has determined that the actuator is indeed faulty and you are going to replace the actuator, you can save yourself some grief by keeping a couple of things in mind.

If your old actuator is still working some of time, you may want to try this. Using a small mirror, adjust the driver’s temperature until the old actuator is as close as possible to the new actuator position.  Remember that the image is backwards and double check it against a point of reference. DO NOT try to adjust the new actuator to match the old one. If the new actuator is connected to the harness in an attempt to do that, it may over travel and stick in that position.

Finish removing the old actuator assembly.

The new actuator generally arrives with the notch in the shaft centered on the middle hash mark. That would be the position you would like for the old one to be indexed at before removal. If it is still working.

In one of the earlier links about testing at the passenger junction block, there is also a method for moving a stuck actuator. I would strongly recommend consulting a wiring diagram and connector pin out specific to your vehicle. GM does move some of the wires in various years and models. 

This one would not move and the system will need to be recalibrated after the new actuator is installed. On the old actuator the notch is slightly past the right hash mark. Also the part number on the two actuators have changed, 52402588 on the old one and 89018365 on the new actuator. If you want to purchase the most up to date actuator for this truck

please click here.

Note the commanded and actual positions on the screen below.  This is the reason for having to recalibrate the actuators.

After the recalibration is done the numbers will be a close match. Not always an exact match though. The reason I am trying to steer you towards aligning the old actuator to the new one is this. You have already had one actuator fail. The rest of the actuators are just as old as the one that failed. If you perform the recalibration procedure, all of the actuators are calibrated and not just the one you replaced. This opens up the possibility of other failing actuators becoming stuck. There are four actuators in all. If you are a DIYer finding these other failing actuators may not be convenient to your finances or HVAC needs. If you are doing this for someone else you need to make the vehicle owner aware of what might happen. Think of DIYer concerns.

Re installing the hush panel is a little bit of a pain in the rear but I did a post that shows how to make it a little easier. Please click here to see.