This 2004 Chevrolet Tahoe came in with the complaint that the air on the driver’s side would change from cold to hot while driving down the road. When it shifted to hot the customer could not get it to turn back cold. Sounds like a faulty air mix actuator to me. I checked codes and sure enough there was a code B0408 for the left air temperature actuator. I checked the commanded position versus the actual position and there was a large difference in the counts. This is only important if you have a scan tool that will access this system. There are other tricks that can be used to test that I will show later. The driver’s or left air mix actuator is located on the lower passenger side of the dash. If present the hush panel has to be removed. This one is easy because there is no floor mounted center console. If you have a floor console please see the information at this link to see how to deal with one screw.
I removed the four 7 mm headed screws and pulled the panel out of the way.
I knew I was changing the actuator, so I disconnected the wiring harness connector and removed the two 5.5 mm headed screws
Then the actuator simply pulls down. There may be some resistance if the actuator is at the full stop position.
Slide the new actuator into position, install the mounting screws and reconnect the wires. After this was done I recalibrated the actuator with my Tech 2 scan tool. If you do not have a scan tool you may disconnect the battery for one minute. Reconnect the battery and start the engine. The key point is DO NOT TOUCH the a/c controls for at least one full minute. Actually, I prefer to wait 4 minutes because I remember reading that a few years ago and the extra time does not hurt anything. After one full minute turn the ignition off. Restart the engine and check the door operation.
Proper operation can be seen in the data stream in that the commanded and actual positions are at nearly identical counts.
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 next tests must be done with the harness connector plugged into the actuator. The yellow wire is a low reference wire from the control head (ground, 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 the voltage will change up or down depending on the movement of the actuator (between 0 and 5 volts). The dark blue wire 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 and 2.5 volts is a signal to hold 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. Next 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.
Something else you need to know. If you buy a new actuator make sure the part numbers match. At the time of this writing the aftermarket (non dealer) application books are incorrect. You have to buy an actuator for the passenger side to get the correct actuator for the driver’s side. Crazy but true. I cannot think of the number of actuators I have changed that have already been replaced by others. If you install the wrong actuator, it will rotate to a full stop and never move again.
This is the box that the actuator I installed came in and the numbers on the actual parts matched (52402588). The short number is 15-72971. Long number 89018365 and it is listed as the passenger or top air mix actuator. To order this part please click here.
It sounds like a faulty actuator. What normally happens is the a/c control head sends a signal to the actuator and looks for a response. When an incorrect response is given the control head tries again and again. after repeated attempts the system goes into a stall mode and will not move any more until the next key cycle and then the whole process starts again. This can be determined using a scan tool or with the testing instructions I have given in the repair post.
I have a 2004 Tahoe. From time to time, it will start with cold air then start blowing hot air (center & driver side only). I can turn off the car and restart it & it fixes it for some time. Do I have an actuator problem or does the system just need recalibrating?
You can rotate the door shaft that the actuator connects to when it is mounted in place. Should be able to do this with your fingers but you could also use a pair of pliers. Just don’t scar up the shaft.
Sparky, As I look at the molded position marks on the bottom side of the actuator, the replacement actuator I just bought is in the “center” position, but the actuator I removed is in the “right” position. How do I get the new one lined up so it will slide into place?
Thank you,
Sorry the pictures are lost and we will have to wait until one of those problems comes back into my shop. To answer your question somewhat. The passenger temperature actuator is located on top of the heater-a/c case. It is difficult to access but not impossible. I did a post about changing a recirculation door actuator and will include the link address. Once you get the dash to that state of disassembly, you will have to remove all of the top support brackets. Some of the screws that hold the duct work will need to be removed. If I remember correctly the lower dash mounts only have to be loosened. Then you can come in through the airbag opening and remove the screws from the backside of the actuator. The actuator will be behind the rightmost driver’s side vent. The airbag switch panel or blank panel under the vent will need to be removed to see it. Until I can get another of these problems in to do full documentation, I would suggest subscribing to Mitchell or Alldata to get the particulars on removing the dash cover. There are links on this site to both.If you need more infor please contact me through email sparkysanswers@gmail.com
http://www.sparkys-answers.com/2010/08/changing-recirculation-fresh-air-door.html