Hey guys this question is going to be for the GM guys on the board.
I have an old 98 Lesabre, and it runs and drives great. When I first got it I had to do the Vacuum line mod on the programmer to get the HVAC to blow out the face vents. That was the best $1.60 and 30 min I spent on a car 
That mod still works and was done about 1.5 years ago, the ENTIRE time i have owned the car the temp blinks when I start the car, but the HVAC has always worked fine so I paid no attention to it. That is until 3 weeks ago when I had to replace my intake manifold. I disconnected the battery without turning the system to “off”. I have been doing a bunch of reading online, and it seems I may have thrown the system’s sync off by doing this.
Right now my problem is this, colder air coming from the pass side then the driver’s side. When I start the car it will seem synched for a few seconds, then it will start blinking and both vents will go FULL COLD, eventually it brings the temp back up the d-side gets hotter than the p-side. I have done the following:
- gone through AT LEAST 50 on/off cycles
- Removed the 9c fuse to try to reset
- Pulled down the glove box door and watched both the upper and lower blend doors go through there whole range of movement (which they do)
- Tried to re-sync by pushing the temp full hot, then full cold a few times in a row.
Besides getting this scanned by a tech 2, which is my last resort, is there anything else I can do?? Did I miss anything??
Thanks again
JOSH