I have a 05 tahoe and the rear heater problem is will known at the dealer! i don't know why they don't do a recal on it. when i had them take a look at it they told me it was going to be $500.00 i already took it apart to find out the issue i test the wires and was geting the signal from the front rear contrals to the back before it goes into that little cpu unit thing back there the output signal was just sending a cold postion to the acuator and wouldn't tell the acutore to switch. i tested the acuater to make sur it work and it did when i send it a signal manualy it will switch but something in that darn little cpu unit back there isn't working. the signal i recieved from the front i bipassed the cpu straight to the acutor so know i can switch it from hot to cold just not to the mid rang temps. the dealer said that they would also have to reprogram the cpu back there to work with the acuators, that maybe why when some of you switched acutor and then put them back the no longer worked. hope this may help and if anyone could help me to find out how to reprogram the stupid thing with out paying the dealer $250.00 that would be awsome

 

Sorry to resurrect an old thread, but I'm having this same issue with my newly purchased 03 Tahoe. I pulled the actuator and checked everything to verify its functionality. When its plugged into the connector, the motor just travels back and forth between a small area and doesn't stop until i mount it back into position. At that point it seems to just grind itself to a stop because the damper wont go any further. I'm not sure if its the actuator that's the problem or if its the signal its getting from the HVAC control panels. Is there a parts place online I could get a new accuator to try and then return it if that's the not the problem? Any help would be a appreciated. Thanks!

 

And i'm having the same problem on my 2004 Tahoe. The start of this post suggests that there is a known problem here? And the post from riptide (2 entries above) seems to confirm it. I'm just wondering if there's a good "how-to" that we could follow for the diagnosis of the problem (is it actuator or cpu?) as well as the repair of each?

And did anyone find out if there's a way to re-program the CPU for the do-it-yourselfer? I had a Volvo that you followed a series of ignition on-off cycles followed by turning the floor/vent/defrost switch a certain way which made the cpu "re-learn" what it was supposed to do...

 

Yes you can order Chevy parts from www.gmpartsclub.com and if it doesnt work I believe they have a 30 day return policy, check the site to be sure. Try giving them your vin# and you will probably get the right part. I had to replace the actuator in a buddys vehicle recently.

 

I'm gonna update my previous post for those that search this thread in the future, and that is that I pulled apart the plastic covers to get at the rear heat assembly. Once exposed I found the actuator and unscrewed it from its mounting points (3 screws). I was then able to move the flap inside and that moved freely and allowed heat or cool air to flow. I played with the actuator a bit and couldn't get it to work. ( In fact, it appeared to have travelled right to the very end of it's geared run when I opened it up). So I went to the local dealership and got a replacement ($162, part number " 89018375 Actuator 092800 " I plugged it in and screwed it back onto its mount and now it works fine.

 

...And I spoke too soon. Worked for a day, now I'm back to the same problem. Anyone?

 

So most of these cases are pointing to a calibration issue in the HVAC controls rather than an actuator so it seems.

 

any updates on this? Its getting COLD here in IA and I'm hoping to take mine to a local shop sometime this week to have them check the calibration before I go spend $100 on the actuator.

 

My surfing around found the following post on another board (apologies if I've violated a rule for the forum, please email me and or edit the post if I have)...

http://www.fullsizechevy.com/forums/...wing-cold.html

If you read down, you'll see someone posted a technical service bulletin on this matter which says to replace the little black box/computer controller first, and then if necessary, replace the actuator. The parts numbers are there. I replaced the actuator first which now may or may not be damaged because I didn't replace the black box. I've purchased the black box but am still trying to find out if there are body/chasis codes that have to be read and reset before I install the black box.

I don't know for sure and am still trying to find out one way or another, but, apparently, the usual code readers you can buy for $100 to $200 don't read chassis codes, they just read engine management/engine electronics/pollution control type codes. If anyone out there can tell me, I'd appreciate it. I'm also hoping to get in touch with a friend of a friend who used to work (just laid off) for a Chevy dealership.

Bottom line, I would suggest that you will be replacing the black box FIRST, and then the actuator, or both at the same time. But since I tried replacing the actuator FIRST, and it now doesn't work (and may or may not be toast), go with the black box first.

AGAIN, I'M NOT A SKILLED MECHANIC, so I don't know. That's why I'm still hoping to find a GM tech who's reading these forums who can tell me for sure.

 

thanks, i just ordered the control module from amazon for $63 shipped. I'll try it out first and then do the actuator if that doesnt do it. I figure that's still cheaper than taking it the local chevy dealer.