ynk1121

1995 with the automatic climate option. If I turn it to 60F the fan blows but the air isn't cold. I don't hear the compressor kicking in at all. Off button shows no flashing light above it. I held the arrows for 5 seconds and pressed the auto button and it just shows "00".

My question is: If this is caused by a low freon situation, would it 100% have a code? I don't have the gauge to check pressure. Anything else I can check?

colo63sw

Did they have the automatic climate option n 1993? My AC/heating isn't working good at all.

ynk1121

Yeah, the thread I found said 90-96. I think they called it the C68 option. If you can set a specific temperature then you have it. When you put the car into run, the light above the off button is supposed to blink if there is a code stored. Holding the up and down fan arrows until it shows "00" and then pressing the auto button is supposed to show the code number.

I get nothing but "00"s and no blinky light so I don't think I have a code to work from.

colo63sw

Thanks for the info.
I can set a number so I must have it. Mine is wacky; at 90 deg heat works fine, but if it set it to 85 & below it starts putting out almost outside temp air. The AC doesn't work (clutch doesn't engage). And with system off, hot air comes out the defroster.

Thanks again!

pcolt94

A system with low Freon usually cycles the compressor on and off al lot. The system would have to be nearly empty with a massive leak to have no Freon in it to not close the cycling switch and turn on the PCM electronics and compressor. That’s where gauges would tell you for sure. Static pressures are about 70 to 100 psi depending on ambient temperature

The simplest thing to check is the cycling switch which is on the pipe coming out of the evaporator. If you remove the connector and jump it out and if the cycling switch is bad, the compressor will start. If it does not start then the problem is elsewhere and the troubleshooting gets more complex.

Getting the codes for the A/C is a nice thing but usually not to useful unless you have a FSM and know what the counts mean and how to use the information. A "09" code is low Freon and I don’t know what the criteria is to give a code. How low is low, many times a low system will still work, just cycle a lot. So if there is no code it probably has enough Freon in it to work at some level........I guess.

colo63sw

Thanks for the info.
I tried what you wrote and I get a code of '09'. Pcolt94 just happened to mention what '09' meant. Thanks Pcolt94!
I still doesn't explain why the heat is so wacky and why the defroster is on all the time at full 90 deg temp.

Silver85

This may or may not help but I'll throw it out there.....

Same thing happened on my 2003 Avalanche when the temp sensor for the interior failed. Since it didn't know what temp it was, the dampers would default to full hot when the temp was set to 90 and full cold anything below that.

colo63sw

Anyone know where the temp sensor for the interior is located in a 93?

Silver85

Im not sure but I did find a pretty cool video on that might help. You could cycle through the codes and see what kind of temps the sensor is reading?

colo63sw

Great interesting video, thanks for posting. I will need to study it more when I’m not at work.

Sorry ‘ynk’ if I hijacked your post, seems like I am getting more help with my issue than you are.

pcolt94

The sensor is on the passenger side behind the A/C vents. But I would not compare the symptoms or workings of electronics to an Avalanche. The corvette also has a sun sensor and outside air temperature which all feed into the programmer as well.

pcolt94

So that probably means it's not low on Freon to prevent the compressor from coming on. Check the cycling switch as I described and then go from there.

desertmike1

To all of you guy's.. a Scan tool will give you both the PCM "Command" status, and A/C High pressure transducer reading's in (PSI) you don't need a Gauge set to check Refrigeration Static pressure..

Don't jumper anything out until you have at least checked for a Freon Charge, running a Compressor on a low/empty charge can damage the Compressor do to lack of lubrication.

pcolt94

This is true, as long as the system is equalized the high side pressure sensor will tell you the static pressure. Not all people have a OBD1 scanner and a set of gauges is nice to have so when you get it going you can look at low and high side and add gas to the system if needed. You can pick up a set of gauges for $40 - $60.

Probably not a bad rule of thumb.
In this case there is no error code for low Freon from the control head so if there are no gauges and scanner data at this point in time, a simple test would be a start to move forward.

There is always oil in the compressor and bypassing the cycle switch for a moment will not hurt the compressor for a test. Granted don’t leave it in there for the long term this is just to find out if the switch is bad - peace.

John S 1961

put some gas in it

pcolt94

He tried, he can't because the compressor is not running.

That's what most of these posts are about.

ynk1121

Ended up being low refrigerant. It was just barely reading into the low section on the gauge. After a second filling it the compressor came to life. I'm not sure why it didn't trigger a code but all seems to be working now. Thanks for the ideas.

colo63sw, when I first bought my car I only had air coming from the defrost vent. It ended up being the vacuum check valve on top of the engine under one of the plastic "corvette" covers. Like a few dollars and 10 seconds to change.

colo63sw

Thanks for the tip ynk1121! Do you have more detail on the plastic cover on top of the engine? I hope it is the passenger side cover.
The driver’s side cover has the throttle cable pinned to it; what kind of ‘project’ is it to remove that ‘plastic’ cover???

I hope my problems are as easy to fix as yours.

A Peter C4

Just pull up, its on push pins connected to valve cover, to reinstall just line up the clips on the cover with the pins and push it back down. On driver side just pull up carefully on throttle clips and then remove cover or pull up on cover and slid cover to rear with throttle clips in place.