2001 Tahoe Hvac Control Head Or Actuator?

[2001EAYoung]

I have been reading through the forum topics here and elsewhere on the web and I haven't been able to find anyone who has the same issue(s) I'm having with my 2001 Tahoe's front HVAC. The temperature blend door actuator is behaving odd.

 

When the temperature control is moved the actuator doesn't move. The temperature blend door actuator only moves when the control is turned to the either full COOL/COLD or full HEAT/HOT. As it is moving from one end of the range to the other it 'steps' or pauses every 5-10 seconds until it reaches the limit of travel set by the blend door's range of motion. It I turn the temperature control one setting off of full HEAT/HOT, the actuator will continue to 'step' and pause until it reaches the limit of the blend door's travel for full COOL/COLD. In short I do not have any control of the temperature other than full COOL/COLD or full HEAT/HOT, there is no in between setting regardless of where the control is set to. Here a list of what I've done so far:

 

I removed the actuator and opened it up to check for broken gears (there was NONE).

 

I removed the electric motor to test that it was working (it WORKS).

 

I manually moved the blend door to ensure it moves freely (it DOES).

 

I removed the HVAC control head from the dash. I unsoldered the temperature control's potentiometer and tested it with an OHM meter. It tested good at both ends of it's range with NO dead spots in between, it has a nice linear range of resistance.

 

I put the actuator back in and recalibrated the HVAC system as has been described here on this forum and other forums on the web (pulled fuses, disconnected battery, wait the allotted time of 15-30 seconds, reconnect battery, install fuses, turn on ignition, don't touch HVAC controls for the allotted time of 45-60 seconds while the actuators 'reset' themselves).

 

The other actuators appear to work just fine, switching from floor to vent to windshield and the recirculation actuator appears to work as well. When I reset the system I can hear those actuators moving and I can see the temperature actuator move. The temperature actuator quickly travels from one end of the range of motion until the blend door is fully against it's stop. The actuator pauses, reverses, and quickly travels to the other end of the blend door's range of motion until the blend door is fully against the other stop. The stops are the blend door's travel, not the hard stops on the actuator. The actuator then pauses for about 5-10 seconds, reverses and begins 'stepping' and pausing until it reaches the position it started from. After the rest of the system has finished resetting, I've turned off the ignition, waited about 30 sesconds, then started the vehicle and tried to adjust the temperature control. The temperature actuator doesn't move like it supposed to. It only moves as I've described above.

 

Am I missing somethng here?? I've tested/checked out the system multiple times and I still have no control over the temperture setting for the front HVAC. I want to make sure I am replacing the correct bad part that is malfunctioning.

 

Is it the HVAC Control Head or is it the actuator?? or BOTH??

 

Great forum and thanks to those who contribute!!

Erik

[bwlaqua]

i have a similar thing happen to my 01 silverado. the temp would either go cold or super hot. I removed the actuator but kept it plugged in. i noticed it doesnt move the full range of travel. Im going to order a new one when i get paid. I think it might be the circuit board in the actuator. the heat blend actuator is around $35 on rockauto.com. so if it doesnt work its not that much your out. the acdelco one is a little over $50. Try out that and see what happens. good luck to ya.