Hey everyone, I'm in need of help figuring out this A/C system. I own an auto repair shop that did an LS3 swap into this 1989 C4. Our customer wanted everything to work as it should from the factory. A/C, Power Steering, Cruise control the whole 9 yards. This customer has roughly $90,000 into this C4. We originally did the swap for him but he thought we were taking too long to complete the job. Our shop is not designed for these types of jobs. We are a high volume repair shop. We took this job on with him knowing that it wouldn't be priority over customers that need their vehicles for their daily commute or companies (including his) needing work done. It took us roughly 9 months to get it "completed" for him. We had several issues along the way. Originally he wanted us to keep the factory gauges and all. We had a custom engine harness built. Needless to say that was a huge mistake. There was a lot of issues with the harness that we did get figured out over the 9 months. (Mostly pin location) Second was tuning. The tuner apparently didn't understand the difference in 4l60e transmissions through the years and was using the wrong OS to control the transmission (this trans doesn't have a 3-2 downshift solenoid). Once I got that figured out for him, we finally got it tuned and going for him. We had issues with making the a/c system work properly from the start.

Needless to say the customer was frustrated with me as much as I was frustrated with the car. We gave him a running and driving car, but the A/c system wasn't working.

He took it to another shop to have them sort out the AC system as he had lost faith in me. They ended up switching the ECM and complete harness we had made for the car. We used an E38 computer that I know pretty well. They switched it to a E67 computer that I know very little about.

Unfortunately for the customer they too had the same issue I had, except they caused many more issues that caused the transmission to prematurely fail (less than 500 miles)

The car is now back at our shop almost 2 years later. The customer was very clearly regretting his decision to let someone else work on it. - He decided he wanted us to put a manual transmission in it. - I adapted a CD009 transmission from a Nissan 370z to the LS3. This pairs amazing to the factory 2.42 rear gears. It doesn't need a double overdrive like the T56 has and I prefer the way they shift better anyhow.

But here we are again with NO a/c. I have confirmed that all wiring is correct to my Mitchell wiring diagram of the automatic AC head, blower motor control, pressure switches and AC clutch and diode direction. I installed a brand new blower motor control module as I thought that was the issue. I bypass the pressure switches by grounding the light green wire without success. I do this all on manual mode with the temp all the way down to 60.

I noticed this is all solid state stuff. - I'm not exactly the most educated on that stuff. Seems as though there should be 5 volts floating on certain wires then they ground? The car was built the same year I was born, so please forgive my ignorance to this stuff.

The only things not hooked up are the exterior temp sensor and the ECM signal. Everything else is.

Anyone well versed on this stuff that might be able to put me in the right direction? Thank you!

 

Bump for the member.

 

I've unfortunately no experience in diagnosing your AC issues, but would you mind sharing some details behind the CD009 swap? I know it's a thing for the LS swapped Nissan/Infinity crowd, but curious how you handled the c-member mount and driveshaft.

 

Batee.com is has a troubleshooting guide for c4 corvettes. https://batee.com/pages/1986-1989-c6...eshooting-info
86-89 climate control sends a signal to the compressor circuit to disable at full throttle. I believe it grounds the circuit to do so. If it is not connected to the ECM and is grounded the compressor will not run.