My brothers '94 with auto climate control quit. The back light on the module is the only thing that works. Bought a new one from Corvette Central and it is doing the same thing. Took mine out of my '95 and it does the same thing. Took the original from the '94 and put it in the '95 and it works. I am trying to find something on it in the service manual but I am to frustrated and getting no where please help! I also checked the fuse and tried putting the module in diag. mode but it wouldn't go.

 

Even though you checked the fuses, you need to verify with a Volt Meter if 12 volts is at the following fuses.

Open the passenger side door and on the end of the dash you'll see the fuse panel. Remove the fuse panel door and verify the A/C Clutch 10 amp fuse is not blown.

There should be 12 volts at the fuse when the Ignition switch is in the Run position.

There is also an A/C Programmer 5 amp fuse which should have 12 volts at all times.

The A/C Programmer is the Brains for the A/C Control Head.

 

I've got 12 volts at both places. When I took the one fuse out for the a/c clutch my display light on the module went out.

 

I'd say the AC Programmer may be bad.

If you pull the 5 amp A/C Programmer fuse on your vehicle, (leave A/C Clutch fuse in) do you get the same symptom as your brothers car?

 

Agree with above - You could verify ignition voltage at the panel - should be the brown wire - and ground, but with it lighting up, both are probably ok. Then, check the 5 volt reference from the Programmer, green/black. Communication is over the Data Lines, green, but about all you can do is verify that they're not open. Otherwise, a bi-directional scanner can send the same signals as your Panel via the CCM link and if the Programmer doesn't engage the compressor, etc, it's shot. However, with a new control panel that works just fine in another Vette, got a feeling you allready know that.

 

On a '92 (not sure about yours), the C68 climate control head and Programmer communicate over the "Comfort and Convenience" serial-link that is not normally connected to the ALDL serial-link.
To use the bi-directional scan-tool to trouble-shoot and simulate signals, requires temporarily hooking a jumper wire from the "Comfort and Convenience" serial-link to one of the ALDL serial-links to allow the scan-tool (that plugs into the ALDL connector) to communicate with the "Comfort and Convenience" serial-link. This procedure is in the shop manual.
These two serial-links should NOT be left connected afterwards -- can cause problems.
So, to make it convenient, I connected them together through a switch. Now, I can simply throw a switch to connect them when needed to trouble-shoot the C68 climate control. Otherwise, the switch is off.

Once this connection is made, you can monitor the commands (in English) sent from the control head to the Programmer to determine if the correct command is sent. And, you can simulate the control head commands with the bi-directional scan-tool to see if the Programmer responds to these commands. Plus, you have the usual monitoring of trouble-codes and data parameters.

A similar setup can be used to monitor and trouble-shoot the Bose radio control head (in the dash) and the radio receiver (under the glove box) that communicate over a serial-link.

Tom Piper