Last year my air worked fine, this year after only using vehicle 2 times the heater air control inside car blinks sometimes then goes back to normal operation. The problem is the compressor for the air won't engage. The unit is charged, heater works. Why won't the air compressor engage? Checked the fuse inside vehicle thats ok, are there any other fuses?
Hello Chuck, Sounds like you've got an electronic control head (RPO C68) rather than manual (mechanical -- C60) control. Initial hunchs would be a loose connection between the head and the compressor clutch, a problem in the control head or an interior temperature sensor (location varies with body type.) Confirm body style and type of control and we might come up with some better specifics.
Couldn't tell from the other post if this was an electronic controlled unit rather than manual. If electronic it could be the inside temp sensor or wiring -- up over the cargo deck (manual control doesn't have that.)
Other problem with the '89 electronic controls was corrosion on the connectors to the control head. That was more of a problem in high-humidity locations where condensation in the cockpit was a problem. Gotta run to make. When I get back tonight I'll pull the shop manual and get some more info.
Just got back (the C5 saw its first rain since I bought it) and checked the shop manual. The compressor control circuit is entirely different between the C60 and C68 options. The compressor is 'hot' all the time and is supplied from the A/C fuse. Control is in the ground circuit, turned off-on by the Blower Control Module (BCM). That module is behind the instrument panel on the left-hand side of the evaporator housing.
Two pressure switches, a high limit switch and a pressure cycling switch (comes into play if the evap ices up) signal the BCM. The A/C & Heater control head gets signals from the inside air temp sensor (over the cargo deck) and an outside air temp sensor.
The ECM doesn't control the compressor. A signal from the A/C to the ECM causes the idle speed to increase and the ECM turns on the coolant fan. As I read the diagrams, the only ECM problem that could affect the A/C compressor would be a short at its input. That would probably smoke the ECM and blow the A/C fuse. So, I'd forget the ECM for now.
Sounds like you've got A/C - Htr. control head problems or temp sensor problems. The troubleshooting tree for the C60 option is pretty easy but the tree for the C68 option is too lengthy to play with here.
The shop manual has a good troubleshooting tree and schematics. If you can't get a copy (sections 8A-62 and onward.) I can burn the pages and mail them to you. Drop me a snailmail address at my email address. Please confirm though that you've got the C68 option rather than the C60 option.
Hello
I had a similar problem last year with my 89. I had GM verify it and 1 hour later they told me what my problem was. It turned out to be my ECM was shot. It was engaging the compressor and disengaging it, so i was going from freezing to heat. They replaced my ECM and everything has been working fine since.
Good Luck Dan
Hey PJ I want to thank you for your help. I jumped the switch and the compressor came on, I then put the gauge back on with the compressor running and I needed Freon. I put 1 can in and the compressor now engages. The air is cold but I need about 1 more can of freon. Thanks again for all the help now it will be a cold summer for my Baby (1989 Vette). Thanks Chuck
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