Automatic Climate Controls Runs Wild. Opinions?

[WildernessJeep]

I have a built Jeep, but the wifey drives the 2005 GMC Yukon Denali AWD. The A/C has the automatic climate control, with the dual control system (which is as stupid as a "peeing" section of a public pool).

After about 30 seconds of nice cold air, the damn thing goes full hot, full blast. The rear AC continues to blow cold, and they both battle it out at full blast unless you turn the fan down on the front and just live on the rear AC (which sucks in Houston). It did this about six months ago, but disconnecting the battery for a few minutes fixed it. Now, it is constant and won't correct itself.

The interwebs have mixed results. People pulling their dash, replacing actuators, replacing the control unit, body control module, replacing the ambient air temperature sensor; all sorts of things with no clear answer (most posts started with "I replaced my ________, and it didn't fix the problem".)

I was planning on taking this vehicle on an out of town trip for the holiday next week, but not if it is going to run the heater on full blast the whole way. Anyone have any ideas on the actual source of this problem?

Thanks in advance,

Rob

---------- Post added at 06:14 PM ---------- Previous post was at 06:10 PM ----------

Also, there was a small pump sound coming from the drivers side center console that seems to have stopped at the same time. The sound seemed to be a "squeka-squeeka" sound, cycling about once a second. It looks like a small air port is in the console (right next to the drivers right knee). Opinions?

 

[JochenWoern]

I have a built Jeep, but the wifey drives the 2005 GMC Yukon Denali AWD. The A/C has the automatic climate control, with the dual control system (which is as stupid as a "peeing" section of a public pool).

After about 30 seconds of nice cold air, the damn thing goes full hot, full blast. The rear AC continues to blow cold, and they both battle it out at full blast unless you turn the fan down on the front and just live on the rear AC (which sucks in Houston). It did this about six months ago, but disconnecting the battery for a few minutes fixed it. Now, it is constant and won't correct itself.

The interwebs have mixed results. People pulling their dash, replacing actuators, replacing the control unit, body control module, replacing the ambient air temperature sensor; all sorts of things with no clear answer (most posts started with "I replaced my ________, and it didn't fix the problem".)

I was planning on taking this vehicle on an out of town trip for the holiday next week, but not if it is going to run the heater on full blast the whole way. Anyone have any ideas on the actual source of this problem?

Thanks in advance,

Rob

---------- Post added at 06:14 PM ---------- Previous post was at 06:10 PM ----------

Also, there was a small pump sound coming from the drivers side center console that seems to have stopped at the same time. The sound seemed to be a "squeka-squeeka" sound, cycling about once a second. It looks like a small air port is in the console (right next to the drivers right knee). Opinions?

Have the dealer diagnose it for you, but my guess would be a bad actuator or temp sensor.

 

[scottg918514]

Bad blend door actuator. The temp blend door actuator is under the glove box. You can get a new one at auto parts store for about $130, maybe cheaper online. I had same issue in 2003 Tahoe Z71. Getting to the bolts (3) can be an issue. One, I used a 5 mm Allen but in a 1/4 in ratchet.

 

[WildernessJeep]

Bad blend door actuator. The temp blend door actuator is under the glove box. You can get a new one at auto parts store for about $130, maybe cheaper online. I had same issue in 2003 Tahoe Z71. Getting to the bolts (3) can be an issue. One, I used a 5 mm Allen but in a 1/4 in ratchet.

Got a write up on it? It seems to be a pretty common issue with these trucks. I looked under the drivers side dash, and that looks like a bunch of no fun. You say it's on the passenger side under the glove box?

 

[NathanJax]

Got a write up on it? It seems to be a pretty common issue with these trucks. I looked under the drivers side dash, and that looks like a bunch of no fun. You say it's on the passenger side under the glove box?

you can search in the interior section or in the tech section for write ups.


here's one of them from the tech section
http://www.tahoeyukonforum.com/forum/showthread.php?t=15787&highlight=actuator

 

[JochenWoern]

Bad blend door actuator. The temp blend door actuator is under the glove box. You can get a new one at auto parts store for about $130, maybe cheaper online. I had same issue in 2003 Tahoe Z71. Getting to the bolts (3) can be an issue. One, I used a 5 mm Allen but in a 1/4 in ratchet.

I had a bad actuator door in the rear which caused my rear to only blow hot. After I changed the part and the door is functioning properly, all works now great.

In general I agree that it as well could be a bad actuator door, but I question the earlier statement made:

"It did this about six months ago, but disconnecting the battery for a few minutes fixed it. Now, it is constant and won't correct itself".

Disconnecting the battery will definitely not fix a broke door, but it could recalibrate a bad actuator for a little while, .... NO?

 

[WildernessJeep]

I replaced the drivers side actuator. It was very simple, and the technical write ups from this site certainly helped. You were right; the third screw was a PIA.

The new actuator is working fantasticly, no problems. I'll be driving to southern Mexico next week in it, so I'm glad I have working A/C again.

 

[JochenWoern]

I replaced the drivers side actuator. It was very simple, and the technical write ups from this site certainly helped. You were right; the third screw was a PIA.

The new actuator is working fantasticly, no problems. I'll be driving to southern Mexico next week in it, so I'm glad I have working A/C again.

EXCELLENT!

Glad it all worked out and you were able to take care of the problem.

 

[WildernessJeep]

So while I was picking up the new actuator, the service tech happened to come to the counter. His theory was (correctly) that I had recently disconnected the battery without turning off the A/C first.

Apparently, when the actuators get older, they "forget" where they were when the power comes back on. They then try to move even further in the A/C direction, stripping out the motor inside. So, the lesson learned from all this is:

TURN OFF YOUR A/C BEFORE DISCONNECTING THE BATTERY.


Just trying to help keep someone else from suffering in the heat.

 

[kses123]

There was a software update in 2006 for the HVAC module to prevent the actuator from "over-traveling." I just had mine updated at the dealer a few days ago to prevent another actuator from dying.