The temperature doors are controlled by actuators. When the actuators wear, their feedback values to the control module become out of range and the computer will shut them down. GM has developed new software to correct this problem. You can have this software downloaded at your GM dealer for minimal charge. Certainly cheaper than replacing actuators.
What is approximate typical charge at dealership to update this software?
Should be less than $100.
Took the Tahoe in to local Chevy dealer, described problem, mentioned software update. Service Advisor said he was not aware of the software update. I told him there was a TSB on it, he said "I doubt a software download is going to fix your problem- you probably need a new blend door motor, and there are actually two, and they could both be bad." I insisted that they try the software download. They brought it in and hooked it up to the computer- came back and said "we tried resetting the computer, but that didn't work- you will need to make an appointment to bring it in and leave it with us, so that we can diagnose/repair". So my questions are- (1) Is there any chance that they didn't actually download the software? (in other words, am I about to get screwed?) (2) If the software update isn't the fix, what's next? (blend door actuator?) (3) Is whatever is next something I might want to try to fix myself, or is it too complicated? (I am reasonably mechanical- I changed out the blower motor about a year ago). thanks for your help.
Dave, checked coolant level and it was low- added coolant and presto- everything seems to work great! Now I just need to find my coolant leak. Thank you so much for your help. I am not at all confident that the dealership wouldn't have gone ahead and given me the new actuators. Anyway, thanks again for your help.