This 2006 Chevrolet Trailblazer came in with the complaint that the blower did not work at any speed. This repair applies to 2002 -2009 Chevrolet Trailblazers and GMC Envoys,2002-2004 Oldsmobile Bravada, 2004-2007 Buick Rainier, 2002-2008 Isuzu Ascender. The parts are the same but positions may vary for 2004 and 2005 Chevrolet SSR. All with manual A/C controls.
This Trailblazer has dual zone, manual a/c controls as seen in the picture below.
Since this is a very common problem I went straight to the blower resistor assembly. It is located under the passenger side of the dash. To access it the lower hush panel has to be removed. Two 7 mm headed screws are used to attach the panel to the bottom of the dash.
Once it is down there are some wiring connectors that have to be taken loose along with the satellite radio module. Not all vehicles will have this module.
With all of that out of the way, I could now see the resistor and the burnt harness connector attached to it.
A little different view. The red wire is visibly damaged.
I unbolted the resistor assembly by removing the two 5.5 mm headed screws.
I had to use a screwdriver to pry the connector loose from the resistor assembly.
The damaged connector.
As usual the red and black wires were the main wires affected. The needed parts are available at www.The-Electric-Connection.com . Please click here to order.
Now, it was time to splice one wire at a time. I started with the red wire and made sure I applied the heat shrink tubing as this wire has power on it all of the time. I did not want to blow the fuse or remove it either.
Stagger the joints.
Reassemble and this one is done.
Testing is as follows. Disconnect the 7 wire harness connector and inspect. If there is any sign of heat damage replace both parts per above instructions. If there is no sign of heat damage then check the following. With the 7 wire harness disconnected check for power on the red wire. It should have 12 volts at all times and it gets it’s power from the 40 amp blower fuse in the under hood fuse box. Next with the key on check for 12 volt power to each of the following wires as you move the blower speed switch from low to high. Yellow / low, tan / med 1, lt blue / med 2, purple / med 3 and orange / high. Remember, this test is done with the key on and the seven wire harness disconnected. Other than the red wire having power at all times, only one wire at a time will have power on it, during a proper test. If there is no power to any of these wires during the test , check the fuse in the driver’s interior fuse box. If only some of these signals are missing, you will need to inspect the blower speed switch and related wiring. Also you should do a drag test on the terminals to check the spring tension. Please click here for more instructions.
- Terminal “A” Tan = Speed 2, power through blower switch from HVAC fuse
- Terminal “B” Yellow = Speed 1, power through blower switch from HVAC fuse
- Terminal “C” Purple = Speed 4, power through blower switch from HVAC fuse
- Terminal “D” Lt Blue = Speed 3, power through blower switch from HVAC fuse
- Terminal “E” Black = Blower system, ground at all times
- Terminal “F” Orange = Speed 5, power through blower switch from HVAC fuse
- Terminal “G” Red = Speed 5, Constant power from BLWR fuse under hood
If all of the tests above are okay and you want to go a step further, place a test light or voltmeter in the wires going to the blower motor. If the light comes on or you have a 12 volt reading, the resistor and wiring are okay and the blower motor is faulty. This can also sometimes be confirmed by bumping the blower motor with the switches on. If the motor starts after bumping the motor is faulty. One can also remove the blower motor and apply 12 volts (power and ground) directly to the motor. Be careful though the motor will tend to jump and roll all over the place. Hold it firmly and be sure you are clear of the impeller as it could hurt you pretty easily.
One other note. If you have an amperage gauge, test the blower amperage draw while it is mounted in the blower case. Turn on surge amperage could go up to about 28 amps. Amperage draw at high blower should be in the 18 to 24 amp range. The lower the better. Restricted cabin air filters (if present) and dirty evaporator cores will cause a blower motor to draw more current while reducing air flow volume. These two conditions combined will significantly reduce the life of any blower resistor.
Sounds like you disconnected your battery to do the a/c work. If so that cleared the learned memory in the PCM and now it thinks everything is brand new again. It will relearn in a few days/weeks of driving or you can clean the throttle body of excess carbon build up. Use throttle body cleaner on a rag and wipe it clean. DO NOT SPRAY it into the throttle body.
Speeds 1-5 quit on the blower for the a/c. Changed the resistor and now a/c works. But now getting power surges. When at idle the vehicle stales when the air is on. It doesn’t do it with much notice when the air is off. Thanks for the help.
The control head does not provide the signal voltage. Instead the blower speed controller has a five volts signal at the off position. When the system is activated a ground is sent to the blower speed controller on the purple/white wire. That ground is varied and will reduce the five volt signal. The reduction of the five volt signal is what is interpreted by the blower speed controller to vary the blower speed. Also when checking for power at the blower motor, all of the wiring harnesses must be connected. Both of the voltmeter test leads must be connected to the wires at the blower blower motor. I do not recommend using chassis ground for testing voltage at the blower motor, at least initially.
i have an 07 TBSS with digital controls..im having the same issues, on the three wire plug going into the resistor module i had 12 volts, the middle wire which said is the signal was 0 volts. I checked voltage coming out the resistor module going to the blower itself and had 8.5 volts with the blower set almost top speed. Do i have a bad motor? if so why am i not seeing signal voltage going in the resistor module..is that a sign of a bad a/c control unit too?
This fix worked like a champ for my ’06 TB. Replaced harness and pack and all is well. 1 hour job. The link for the parts is great and provided everything I needed to do the job. Thanks!