A/C Problem
Thread Starter
Intermediate
Joined: Apr 2018
Posts: 30
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A/C Problem
Hello!
I´ve problems with my A/C in my LT-1 1992.
The C68 works fine. There is no blinking LED and no Trouble codes.
ECM becomes A/C request from C68 and A/C Pressure Cyclng Switch. Also the A/C Pressure Sensor is ok - 1,5V 150Psi to ECM.
But the ECM don´t acivate the A/C clutch.
When i make some tests with my Tech1, the A/C clutch get the Turn On Signal and the A/C compressor will run for a few of seconds.
I read in the Service Manual that the ECM need follow conditions to activate the A/C clutch: No WOT, RPM lower 5100, A/C Pressure Switch between 1-492Psi, IAT lower 151°C, CTS lower 124°C, Oil Temp lower 149°C and correct Voltage 12V.
Is it possible that my ECM have a defect also when i can make the test runs with the Tech1 positive? Any other ideas?
Best regards
Juergen
I´ve problems with my A/C in my LT-1 1992.
The C68 works fine. There is no blinking LED and no Trouble codes.
ECM becomes A/C request from C68 and A/C Pressure Cyclng Switch. Also the A/C Pressure Sensor is ok - 1,5V 150Psi to ECM.
But the ECM don´t acivate the A/C clutch.
When i make some tests with my Tech1, the A/C clutch get the Turn On Signal and the A/C compressor will run for a few of seconds.
I read in the Service Manual that the ECM need follow conditions to activate the A/C clutch: No WOT, RPM lower 5100, A/C Pressure Switch between 1-492Psi, IAT lower 151°C, CTS lower 124°C, Oil Temp lower 149°C and correct Voltage 12V.
Is it possible that my ECM have a defect also when i can make the test runs with the Tech1 positive? Any other ideas?
Best regards
Juergen
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Start with the easy stuff and make sure that you have an appropriate amount of freon in the system. Your car would not be the first one to be low on freon and not throw a fault code.
Thread Starter
Intermediate
Joined: Apr 2018
Posts: 30
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Last edited by juergenc478; Aug 22, 2020 at 05:10 PM.
Thread Starter
Intermediate
Joined: Apr 2018
Posts: 30
Likes: 0
Today i briged/jump the A/C Pressure Cylcling switch and the A/C pressure switch. The A/C will not run.
C68 shows no errors.
The ECM gets the A/C request but nothing happens.
When i take my Tech1 Tester an send the car in permanent Service mode the A/C cooling effect is perfect.
Any other ideas?
BR Juergen
Drifting
Joined: Aug 2019
Posts: 1,339
Likes: 225
OK, so it's not a pressure problem. You should trouble shoot the connector to the ac clutch on back to see where the open may be. When the a/c is turned on, do the fans run? Some systems will not turn on if there is an issue with the fans.
Thread Starter
Intermediate
Joined: Apr 2018
Posts: 30
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My car have a lot of modifications. I use a Haltech ECM for the engine management. Therefore are the fans only connected with Haltech and not with the Corvette ECM. But most of the information/reference signals also get the Corvette ECM (for A/C, ABS, ASR etc.). For this the Corvette ECM have only simulated fans connected - maybe here is a problem.
It seems a little bit complicated but this works for ten years without problems.
BR Juergen
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Thread Starter
Intermediate
Joined: Apr 2018
Posts: 30
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Today i found the mistake why A/C will not run. The Corvette ECM gets no RPM Signal and so the A/C clutch will not engaged.
I changed the distributor sensor plate to 24-2 ignition timing (i changed to single injection). For this i disconnect the signals to the Corvette ECM and use the signal only for the Haltech ECM.
Today i see with my Tech1 that there is no RPM signal in the ECM. Than i remembered i disconnectt the High and Low Resolution signal. So i also connected it to the Corvette ECM and the A/C now works fine.
Many thanks for your help!
BR Juergen