Can anyone help with this?

When I run the climate control on auto, the a/c comes on nice and cold but then a few minutes later the air gets warm and humid like the compressor kicked off. I need to shut the system off, wait a few minutes, and turn it back to 'auto' before the compressor cools the air again.

Right now the weather is nice so no worries, but soon I will be driving in 90-plus... ugh.

Any info would be greatly appreciated.

Rick

Oops... the car is a '90 ZR-1 :-)

 

Is the system throwing any codes?

Go here for a "how to retrieve AC codes":

http://www.idavette.net/tech/c4diag.htm

It may be something as simple as low refrigerant (R-12 freon).

 

Is the green light above the climate control button flashing?

 

The green light is not flashing. Everything on the control panel seems to work as it should.

As for the codes, I have not attempted to pull them as of yet. I will take a look at the codes this weekend.

The car will be in the dealer early next week (I just picked it up and need it looked over a bit) and I am going to ask them to recharge the system regardless of its condition. The car did sit for a while before landing in my garage :-)

I appreciate the help!

 

Of course, this is the day I did not drive the car to work so I can't look at the HVAC codes until this afternoon. Oops...

 

Low or no gas would shut it down and it wouldn't work again until it was fixed - at least that's the design. Ditto for any a/c Codes. Yours works intermittently, the LED isn't flashing, so the binary data stream may not tell you much.

Since you're in CA, a shop is required to give you the operating pressures along with the Center Vent Temp and ambient when obtained. That would help diagnose it so post that info if they don't fix it.

Off hand, sounds like a Low Pressure Switch or Blend Door Problem. Pressure Switch cuts power to the compressor relay to keep the Evaporator from icing up and blocking air flow. Yours may not be doing that or simply cutting power when it shouldn't. Hooking up a Manifold Gage Set will show what it's doing and the Shop should do that.

Blend Door sits between the Evaporator and Heater Core and blocks or mixes air flow. It's controlled by an electric motor and if the link or gear connecting it to the door breaks or strips, the door flops around and you get cool/hot, etc. Removing the blower module on the right side of the Evaporative Case allows you to observe the door to see what it's doing.

All the Controls - Dash and the Processor called a Programmer - can be tested with a Bi-directional Scanner through the CCM or Body Module Link. A dealer should have the tools to do that and it takes all of 5 minutes so it shouldn't rack a big labor charge.

 

Thank you so much for this information. I will be able to do quite a bit of diagnosis this weekend before sending the car to anyone else. I can check the blend door myself and possibly monitor the pressure switch with a scope while actuating the system.

 

Ok, I ran through the blend door reset by disconnecting the battery, and the door seems to be doing its job. The controller was not showing any codes, but I did find that the compressor clutch is not engaging when it should be. The fuse is fine, so my next idea is to find the compressor relay and run a test on it. I have no idea where it is and the wiring from the clutch disappears under part of the plenum :-(

I will see if I can find a schematic and then find the relay.

 

If your accumulater is not cold when the air is on it is not working.

 

I seem to be slow with this stuff, but here is the answer:

After trying everything I could to diagnose this, I ended up bringing the car to a shop I trust. In a short time they found a bad clutch cycling switch, replaced it, and recharged the system. I now have cold air from the system. My decision to bring the car to a shop was a result of my lack of experience with the A/C. Next time, I may tackle more myself.

Thank you to everyone who responded and to this forum for all of the help!

 

Seemed to work out great for you. The cycling switch is one of the most common parts to go bad and easy to diagnose and replace. Getting you a normal charge will get you ready for summer.

 

I'm having the same problems on my 92 and I'm curious where this Clutch Cycling Switch is?.

I checked the cable to the clutch and I meassured 12 volts and the clutchs didn't engage anyway.

 

The switch on my LT5 is on the passenger side near the coolant reservoir. I will post a picture this evening.