I bought my first Corvette 4 months ago and love it. It is in great shape except for AC, and a few minor things. My AC had stopped cooling and I took it to a mechanic. The mechanic told me that it was the compressor and that the system needed to be upgraded. They changed to the new system 134A and I told them my husband would do the compressor change, etc. My husband has replaced the compressor, accumulator, drier, etc. and the compressor still does not turn on. It tried once or twice for about 2-3 seconds each time and that was it. The lights above the AC controls were blinking so we checked the manual. We reset the system after charging, following the instructions in the manual and still nothing. Manual said see dealer if still did not work. Is there a sensor that could be the problem? We now think that the original compressor was not bad since it did the same thing. Any help would be greatly appreciated. Thanks so much!

Melissa

 

Assuming you have the C68 Auto Climate control, a blinking LED indicates a error code is stored. To examine any codes you can do the following.

Turn the ignition On. Don't start the engine.

On the HVAC control panel hold and press at the same time the fan up arrow and down arrow buttons for 5 seconds then release them.

You should see -00 displayed in the LCD.

To see what is stored in -00 press the Auto Fan button once.
The first error code will be displayed.

Here are the numbers that could be stored for system errors.

00 No system faults
01 Temp. door motor circuit open
02 Temp. door motor circuit short
03 Ambient sensor open
04 Ambient sensor short
05 In car temp. sensor open
06 In car temp. sensor short
07 Solar load sensor open
08 Solar load sensor short
09 Low Freon
10 Uart failure

To clear any faults, you need to disconnect the negative battery cable for a couple of seconds then reconnect it.

When the battery cable is reconnected and when you turn the ignition on, the HVAC system goes thru a recalibration process. It takes about 30 seconds. It's done when the blower motor turns on. You can turn off the fan by pressing the off button.

In your case you'll probably see code 09 which would indicate low freon. So if you had the system
recharged and you now get a code 09 it would indicate you have a leak in the system.

 

Your AC Control Head may be bad. Do you have a FSM - Helms Factory Service Manual? It would come in very handy.

 

Or, like mine, you could have a bad low pressure sensor that stores the code even though the sytem is fully charged.

 

It won't run until there's gas in it - the Pressure Sensor - on the High Pressure Line has to give some indication of a charge and with nothing in it, the ECM is seeing 0 volts from this sensor. So clear the trouble code and pull a vacuum to get all the air and moisture out of it. Then let that vacuum suck in the first lb (if you're charging from a tank on a scale) or 12 oz can of refrigerant - and even though it's undercharged, the Pressure Sensor will now be sending some voltage to the ECM. Then disconnect the Low Pressure switch and jumper the harness pins with a paperclip which will keep the compressor from cycling on and off (and rapid cycling or on/offs of the compressor relay is one of the other things the ECM looks for to detect a low charge, so if that starts happening, the Low Charge Code will reset and it isn't going to work again until that code is cleared). Start the motor and put the a/c on high and leave the doors open and block the throttle so that it's running at 1200 rpms. Make sure the radiator fan(s) is on. Add another lb or can. If this is an R134 conversion, aim for a charge that is about 80% of the R12 capacity (look for capacity on the Blower Motor housing) or don't let the high side pressure exceed 2.5 times the air blowing across the condensor - monitor the center vent temp. When done, plug the Low Pressure switch back in but leave the gages attached. Pull the Blower Motor connector and observe the Low Pressure reading. The lack of air flow will cause the Low Side to drop and the Low Pressure Switch contacts will open cutting off the Compressor. Note that pressure. For R12, it should be 25 psi. For R134, 22.5 psi. If it isn't right, there's an adjustment screw between the terminals of the Low Pressure Switch. Turn it counterclockwise (no more than 1/2 turn at a time) to lower the cutoff threshold, clockwise to raise it. Plug everything back in; recheck/readjust until it's right. Finally, if this is a conversion, consider reprogramming the ECM to turn on the cooling fans sooner. For R12, the main fan Relay is being grounded somewhere around 200 psi or 2 volts from the Pressure Sensor. The secondary at about 230 psi or 2.3 volts. At higher temps (ambients above 90 degrees), R134 can build pressure quickly so to keep it under control, it's best get both fans cranking around 150 to 170 psi (1.5 to 1.7 volts from the Sensor). Doing this will help to keep your vent temps in the low to upper 50's when it's nearing 100; otherwise, you may find the conversion unsatisfactory when it's really hot.

 

Listen to this man, SunCr. He's helped me diagnose and repair my A/C system many times over. Try to detail everything that was done, and what symptoms show up. This makes it easier for others to pinpoint things to look for. Good luck!

 

What is the AC control head? No we don't have that particular manual, we do have another one though. Thanks for the help.

Melissa