Hey George,

I guess dead was a bad choice of words thank you for asking for an explanation.
Yesterday morning I did reconnect the ac like you asked, when I start the vehicle the ac comes on and cycles on/off quickly. It was 40 degrees out.
Nothing I do inside the vehicle to the control panel does anything.
I do have background lights to the control panel but cannot turn the fan on, cannot adjust the temp, cannot change from head to feet or mix.
So I disconnected the ac again to prevent damage to it from cycling on/off constantly.
I took a 100 mile drive and at no time did any controls on the control module work. 40 degrees when I left and 75 degrees on the way home.
I just happened to be going to pick up another car, not a blazer, repairs I needed a lift for.
We were talking to our mechanic and we just got to talking about this blazer problem.
While I took the other vehicle on a test drive he hooked the blazer up to a computer diagnostic and told me the control panel was needing to be replaced.
He said the control head was sending a command signal to the compressor to turn on even with the vehicle off.
When he disconnected the control panel the signal stopped.
Does that make sense to you? I hope I explained what he said correctly.
Thinking I should just try a new module based on his diagnosis?
Do you have any testing you think I should still do with your guidance?
Either way thank you for your kind help.

 

I asked you to reconnect the compressor to make sure that it was still getting the signal to turn on which it is. The next step would have been to find out if the erroneous request for the compressor was coming from the HVAC module or somewhere else further down the line towards the compressor. The mechanic had a proper scanner that can read GM codes and module status so he was able to do what we needed to do with a multimeter and that is look for the compressor command out from the HVAC module. If you want to confirm then measure the voltage at the module on the lt blue wire on pin D8 on the connector with 9 wires going into it.


George

 

George any suggestions where I could find this part?
I would prefer a new one, but would take a high quality used one.
I will start a new thread asking about finding parts, but would like your opinion about where you would try to get one.
Thank you.

 

For stuff like this I do a saved search on eBay and get a daily email of all new listings. I eventually find a good used item or someone clearing out new old stock.

George