Pontiac Repair: EXT TEMP light blinks, diagnostic check, trouble code

Question
I have a 1996 Bonneville SE 3.8L V6 SeriesIII. The keys were left on and the battery ran down. After recharging, the EXT TEMP lights blinks for several seconds after I crank the motor. The Owners Manual said to take it to a dealer for a diagnostic check. I did that but was told nothing showed up on the machine. I was told that I was low on Freon. I left still not knowing why it blinks. The next day I set the temp at 60 degrees but the air was very hot. I took it to my mechanic. He recharged my freon and put a new thermostat in.(the old one was stuck open). On my way home I put the temp on 60. Again it was very very hot and very cool when I set the temp on 90 degrees. And of course the EXT TEMP light still blinks. I would think the dealership could find this problem. Sorry to be so long winded.

Answer
Hey Mark:

No all the information given the better it is. If that diaplay is blinking there is a trouble code stored in the HVAC control head. Take it to a differnt dealer that has a clue! that ligh blinking means ther is a fault in the system it could be a temp sesnor issue, A door position issue, Low on refirgerant issue. That are a lot of things this could be but the first stem is to take it to a place that knows what they are doing. A gm scan tool will pull out any stored codes in the system and then the technican can go from there.

Good luck :)