A/C stopped working in the fall. The heater seemed to work ok over the winter without the A/C. This spring I noticed that even with the Climate Control turned off I was still getting warm air thru the floor.
Took it to my mechanic. He said the compressor was shot and the programmer was not working right. He recommended not fixing it since the car is so old and has 200k miles on it. (He is not a member of this forum and apparently he does not know a true Bonneville fan never surrenders).
I told him to replace the compressor and I would take care of getting a programmer. When I left his shop cold air was blowing out the defroster but I could not get it to come out the dash vents.
I bought a used programmer and installed it. Wham! just like that I have air coming out whatever vent I desire! Wait not so fast! The air doesn't seem to be as cold as it should be. ??? Go read the forum. Could be the actuator. Sure enough the blend door is not moving. Take it all apart again remove the actuator , disassemble it. Sure enough the plastic gear in the actuator is broken. Call Rock Auto, get and install new actuator . Sure enough programmer moves actuator back and forth as it should , problem solved!!
Not so fast! the temp light flashes for 60 seconds when I turn it on and the compressor does not seem to come on. Took it back to the mechanic to see if it is properly charged. He checked the Freon looks good. He removed the battery cable for a minute to reset it and boom! it works great, cold air comes out any vent that I desire. The next morning no cold air and the temp light is flashing again. Okay back to the forum. I read every post on the subject back to 2009. Swapped the exterior temp sensor with the one in the Park Ave ( known good part) . nothing changes. Take the dash apart and clean the interior temp sensor (it was filthy, that'* got to be it!) Still no change. Its a good thing I love this car because otherwise I would not be posting here I would be calling the wrecking yard. If any of you has an words of wisdom I am all ears. Thanks

you check the two under floor ground busses? they have been known to cause weird issues

https://www.gmforum.com/electrical-1...1999-a-303224/

I will check the ground buses. Thanks!
Drove it to work this morning. Outside temp was 55 degrees. EEC was still set to A/C mode temp set at 60 degrees. With a thermometer in the vent I measured the air to be 60 degrees. Seems like the interior temp sensor is working and the blend door is adjusting the temp properly. Moved the temp setting from 60 to 68 degrees. The output of the vent changed from 60 to 68 within a few seconds. That seems to be working right. Why won't the A/C kick when its warm?? What tells the compressor to kick in? Is that a function of the programmer or the head unit?

Checked the ground busses. They look like brand new. I put a little dielectric grease on them and put them back together.

i dont have time to go through the diagrams now but mine comes on by itself, the only way to get it to turn off is hit the a/c button. i imagine there is a output to the pcm that says call for a/c, then the pcm controls the fans and compressor output

http://gmsi.gc.maricopa.edu:9001/si/home.do

I finally got it fixed! After checking and double checking everything I finally bit the bullet and purchased a brand new programmer. Apparently the used programmer I bought was bad. I attached some pics that I thought might be helpful to others.
I made a tool to reach up in there and insert the plug in the actuator. The tool is made of #9 ceiling wire (wire used to hang suspended ceiling grid in commercial buildings). The plug has a friction fit in the tool. The second tool is used to hook the plug and release it from the first too once you have it in position in the car.
There is a pic of the actuator showing the broken gear. I had already purchased a new actuator so I installed it but , it looks to me like you could reposition the gear 180 degrees as shown in the next pic and make it work again. The next pics are to show you how to orientate the parts when you put it back together.
One last thought . I removed the front passenger seat so that I could lay on the floor and reach up under the dash better. It is possible without removing the seat but, removing it makes it much easier.

thanks for updating the fix, and posting the pics im sure they will help someone in the future

im going crazy here. i`ve read alot of threads but i keep trying things and nothing fixes the problem.......

i just put the engine back in my car and the ECC flashes the outside temp and the air goes cold! i can see the actuator arm now that i pulled the glovebox. Everytime i turn the key on or start the car the arm moves smoothly all the way through its range to allow for heat. After about 30 seconds or so, the ECC starts to flash the inside set temp and the arm smoothly goes back the other way hence, closing the door for heat. i have tried many things, disconnect battery to reset whatever, disconnect outside temp probe( i have about 5 volts coming from the harness and i checked the probe for an open circuit), i have a spare ECC module from my 97 ssei(same part number), i tried that one, no matter what i do, i come back and find the same issue. Cooling system is full and both heater hoses are hot. When the car is warm and i turn it off and restart it, i get heat like normal. After about 30 seconds, BAM inside temp begins flashing and that door closes. When its cold and i let it warm up, the blower motor increases in speed as it should as the car warms but by this time the temp has been flashing and the door is closed,thus allowing no heat.
This car is super clean with only 78k on it. I stupidly let my 18 yr old son drive it once and he spun #1 rod bearing. (in case you were wondering why i had the engine out).

At this point i am going nuts, i love my SSEI and id even offer a reward for the correct fix!!!!! Thanks to all for helping in advance.

Please do not post the same problem in two threads. I posted a (possible) solution in your other thread.