The A/C on my 92 Base model is giving me a problem and am requesting help.
After I start the car, and activate the A/C, the cabin blower comes on like normal but the green indicator above the A/C button begins to blink (which is not normal). The A/C does not cool. Checking the compressor, I see the compressor clutch is not engaging. I checked the fuses in the main fuse panel (at the end of the dash) and all fuses are good. I bench tested the compressor clutch with 12VDC and the clutch activates. I jumped the A/C compressor cut-out switch (thinking maybe freon is low) and this did not allow compressor clutch to engage.
While I was writing this I realized I didn’t hear the radiator fans turn on when I activated the A/C. So I verified that they indeed weren’t coming on with the A/C button activated . I jumped the A-B terminal of the OBD connector to check the fans and they did come on and BTW, no codes were displayed.
I do not have a wiring for the A/C system, so could use a copy if anyone has one handy. Maybe there is a relay for the compressor that I don't know about. I have a Chilton manual and it is vague concerning the A/C system.

 

I think you will find this very helpful:

 

Awesome info. Thanks for that.

 

If it needs a recharge put Freon in.

Disconnect the battery for 10 seconds to reset the ATC.

 

a/c wiring diagrams can be found here and other useful info/videos

http://batee.com/corvette/dcrg/9096_hvac_wiring/

 

I don't believe it can be said that the Battee diagrams are all "inclusive" '90 - '96. All are similar but I doubt all the same. I'd for sure want to be using the correct year diagrams for C68 issues.

 

I did the diagnostic procedure and came up with 09 (low freon). So, can I assume that I will need to activate the compressor clutch by connecting 12VDC so as to be able to add the freon?

 

I had the exact same problem on my '92 and tried putting a charge in and couldn't get the compressor to engage even doing the low pressure jump. It wasn't until I disconnected the battery as mentioned above was I able to get it working again (it clears all the A/C fault codes). Use Churchkey's advice and report back. Good luck.

 

The code nine from the AC control head indicting low Freon is not a direct pressure measurement or amount of Freon in system. It is a duty cycle measurement or how many times the compressor is on and off per minute. There is no set number but only the algorithms in the software which determine this in the programmer.

Removing the battery for a minute should do a re-set if things are locked up. I have had this code when it's cold outside and AC pressures are less and the compressor cycles more. I have never disconnected my battery for this but when having a problem it's wise to follow procedure.

Adding Freon is not the first step ever to do when working on AC. Static pressure should be checked first. The cycling switch should be checked. And if you can get the compressor to run, just look to see when it engages and cycles. Look at the pressures with a set of gauges and see where the cycle point is. Low Freon may make it cycle every 5 seconds which is probably too much at an idle right after the engine is started.

Not saying the code 9 is not correct. But I would do a re-set and start from the beginning. If the compressor runs at least you can see what's going on and if it cycles too much. Adding Freon to a fully charged system is not a good thing as your high side pressures might be too much.

If it cycles to much Freon might be needed but working without a set of gauges is foolish especially when you can get them for under $50 and will work just fine for part time AC work.

 

Copy that guys. I do have a set of gauges and the GM High Side adapter. After making my original post I attempted to connect my gauges for an initial reading. When I pulled the cap on the Low Side, I found the Schrader valve leaking. So I bought this cool tool to replace the valve without loosing any R12 freon. So I spent this afternoon having to remove the power steering reservoir in order to use the tool. The tool worked awesome.
I plan on disconnecting the battery and installing the gauges on Sunday morning to see what my pressures are and installing locator dye to make an assessment. Thanks for all the help and will keep you posted.

 

Update:
I recycled the battery power and the compressor clutch engaged until the system sensed the low Freon. I had to cycle the battery one more time to begin taking Freon and compressor continued to work as normal.
These are my measurements:
Humidity 31% Outside Temperature 97* as per local WeatherUnderground

Initial readings 70Low 70High with engine off
60Low 115High engine running w/compressor off
15Low 115High engine running w/compressor on

Added 12oz of R12 Freon and 2oz of Dye
35Low 225High compressor on, Controls: recirculated air, compressor on, temp-60*, fan-10, 57* measured at top register

It’s working pretty good.
Driving at 65mph at 1500rpm and climate control set to recirculated air, temp-60*, fan-10,
the temps maintained 57* measured at top register.
I’m thinking it is still a little low on Freon, but I want to wait to install more until after I determine if I still have a leak. I am hoping my leak was the Schrader valve that I replaced.
Thanks for all your help, and please respond on my pressure readings.

 

To check pressures:

Vehicle in shade / garage, close the cockpit, interior temps need to be @ ambient temp.

Place a box fan in front blowing @ the condenser.

AC controls @ max cooling.

Wedge the throttle for 1500 to 1800 rpm, read pressures after 5 minutes run time. Run time allows the system to normalize & pull the cockpit temp down.

Add Freon if the low side is below 34# on a 90* day.
High side should run around 190#

Vent temps should be in the 40's.

Good luck

 

If i am already at 35# at 215#, wouldn't that indicate air in the system, as both pressures would rise if i added another can of freon. Correct?

 

Not necessarily.

Not enough compressor rpm = higher low side pressure. This is the suction side

Not enough air flow across the condenser = high side pressure will be up.

Using the previously described method to check the system:
If low side pressure is in the low 30's &
If high side pressure is still up + vent temp is not in the 40's
Freon flow through the system is restricted. Replace the orifice valve & receiver/dryer.

Good luck

 

Copy that. Thanks for your help.

Terry

 

Great video. Leaned a lot. My problem is the compressor is not cycling and my aux fan doesn't come on when it gets turned to A/C. Which I've never understood at what temp setting does the A/C comes on but anyways, where should I start looking? I'm at a loss.