Rear AC Assistance

[davidbeaver1]

I have an 05 Tahoe LT 4x4 and I need some help on how to get the rear actuator calibrated. I started hearing a strange noise coming from the back AC area last week and then found that only cold air comes out of the rear air no matter where the temp control is set. I pulled the rear cover and started watching the actuators to see how they reacted to my inputs of the AC controls. The front actuator was the one making the strange noise, but after unplugging and plugging it back in, it stopped and then started working correctly. The rear actuator that controls the hot and cold air was not working at all so I assumed that is what I needed to replace. I went to OReilly Auto Parts to get a new actuator which they had in stock for $45.99. I plugged it up, turned the rear air system to auto and cranked the truck. The actuator moved like it was trying to calibrate, but then moved into the most upward position and will not move anymore. I disconnected and reconnected the actuator with no luck. I then disconnected the battery, let it sit for 10 minutes, then reconnected the battery and cranked the vehicle. The actuator moved again down and up as if it were calibrating, but then will not move again no matter where you position the temperature on the rear unit.
I have done a ton of research and haven't seen anything related to how to calibrate the rear system and there may not be a need to calibrate it. Does anyone know if there is a process for calibrating the rear actuators? If not, what am I doing wrong?

Part Number for the actuator I purchased in case I don't have the right part... Dorman 604-112 (DA1052) MRY
Thanks for any insight...
Dave

 

[swathdiver]

I have an 05 Tahoe LT 4x4 and I need some help on how to get the rear actuator calibrated. I started hearing a strange noise coming from the back AC area last week and then found that only cold air comes out of the rear air no matter where the temp control is set. I pulled the rear cover and started watching the actuators to see how they reacted to my inputs of the AC controls. The front actuator was the one making the strange noise, but after unplugging and plugging it back in, it stopped and then started working correctly. The rear actuator that controls the hot and cold air was not working at all so I assumed that is what I needed to replace. I went to OReilly Auto Parts to get a new actuator which they had in stock for $45.99. I plugged it up, turned the rear air system to auto and cranked the truck. The actuator moved like it was trying to calibrate, but then moved into the most upward position and will not move anymore. I disconnected and reconnected the actuator with no luck. I then disconnected the battery, let it sit for 10 minutes, then reconnected the battery and cranked the vehicle. The actuator moved again down and up as if it were calibrating, but then will not move again no matter where you position the temperature on the rear unit.
I have done a ton of research and haven't seen anything related to how to calibrate the rear system and there may not be a need to calibrate it. Does anyone know if there is a process for calibrating the rear actuators? If not, what am I doing wrong?

Part Number for the actuator I purchased in case I don't have the right part... Dorman 604-112 (DA1052) MRY
Thanks for any insight...
Dave

Dave, the actuators calibrate with each ignition cycle. A reset can only really be done with a Tech-2.

There are 3 part numbers available for your truck based on its equipment. Can you post up your "C" RPO codes for us?

The wrong actuator will either not work or would run the opposite, delivering cold in stead of hot and visa versa. A quick search failed to turn up what that Dorman crosses to.

Here are your candidates:

15-71845/89018356
15-72971/89018365
15-72972/89018375

My truck uses 2 of the last ones in its rear HVAC system.

https://parts-catalog.acdelco.com/acesCat.php?#

I looked again and on Dorman's website it says that the 604-112 is for the Mode Actuator, 15-73952/89018374 and that will definitely not work in your truck in that position. That's the mode actuator in the driver's footwell, controlling whether or not he air goes to the vents, feet, dash, etc. up front.

 

[OR VietVet]

According to what @915_Tahoe told me about my rear actuators, they are the same part number and would be the 15-72972/89018375

 

[davidbeaver1]

Not sure where to get the "C" RPO codes. Here are the ones from the glove box if that would tell you...

 

[davidbeaver1]

Thanks Swathdiver and MO Vietvet for the info. I took the other part back and used the 15-72972/89018375 as a part number at Advanced Auto. It came up as Dorman 640-111 air door actuator. Plugged it up and it started cycling through as if it were trying to find the limits. After 5 minutes, it was still cycling back and forth, it never stopped. I shut the truck off, restarted and it continued to go from one limit to the other. I changed the temperature to cold and hot air came out but it did stop. When I rotated the temp control knob back to hot, it started that cycling from hot to cold again, never stopping. Evidentially I have the wrong part again...

 

[swathdiver]

Thanks Swathdiver and MO Vietvet for the info. I took the other part back and used the 15-72972/89018375 as a part number at Advanced Auto. It came up as Dorman 640-111 air door actuator. Plugged it up and it started cycling through as if it were trying to find the limits. After 5 minutes, it was still cycling back and forth, it never stopped. I shut the truck off, restarted and it continued to go from one limit to the other. I changed the temperature to cold and hot air came out but it did stop. When I rotated the temp control knob back to hot, it started that cycling from hot to cold again, never stopping. Evidentially I have the wrong part again...

The only thing wrong is that it's Dorman. Get the GM part, search either number for the best price, both numbers are on the same box. It is possible that your controller has gone wonky. You need a Tech-2 or equivalent to pull the internal BCM codes.

Your "C" codes are right there on that RPO sheet, follow them alphabetically. It doesn't matter now, I figured it out on ACDelco's site.

 

[davidbeaver1]

Maybe I'm too stupid to figure this out, but I went to the AC Delco site and the same numbers came up as you indicated in your earlier post based off of my VIN. I've tried the Dorman 604-100, 604-111 and the 604-106 which are the equivalent to the AC Delco numbers and none of them work. Maybe you are right and the controller is gone out. I'm just about done and going to take it to my mechanic to figure out...

 

[davidbeaver1]

So like you said swathdiver, the Tech2 was what was needed. My mechanic reset the controller and everything works as it is supposed to. Thanks for all of your direction and help.