Automotive Air Conditioning Information Forum

I have a 1991 Buick regal, a couple years ago I had to replace the seals in the AC lines because all the freon leaked out. I recharged it with an aftermarket r12/r134a compatible substitute and it worked great.

This year my AC is not working, I checked it with the gauge I got with the kit which only measures the high pressure side and it has too much pressure and I have a computer fault code 66: A/C compressor signal lasted less than 1.5 seconds for 10 consecutive cycles.

Which means the pressure is too low, is my gauge wrong? I replaced the switch on the side of the compressor which I believe is the low pressure cut out switch and recharged it, but where is the high pressure switch located? Did I replace the wrong one?

Get a real gauge kit so you can really check both low and high sides.

I hope - for your sake - that your "kit" didn't have any SEALER in it !

Be interesting to know what refrigerant you are using.

gransport3800 wrote:I have a 1991 Buick regal, a couple years ago I had to replace the seals in the AC lines because all the freon leaked out. I recharged it with an aftermarket r12/r134a compatible substitute and it worked great.

This year my AC is not working, I checked it with the gauge I got with the kit which only measures the high pressure side and it has too much pressure and I have a computer fault code 66: A/C compressor signal lasted less than 1.5 seconds for 10 consecutive cycles.

Which means the pressure is too low, is my gauge wrong? I replaced the switch on the side of the compressor which I believe is the low pressure cut out switch and recharged it, but where is the high pressure switch located? Did I replace the wrong one?

Only high side?

Never seen a gauge with a kit measure the high side only---they measure low side, and when you say there is too much pressure- I can only assume this is with a/c off- since code 66 disables the compressor. and you are merely measuring static suction pressure which would be "in the red" if pump not running. Code 66 says your compressor is cycling too fast due to low charge- so you have a leak somewhere- find and fix leak, evacuate and recharge to spec. The kit gauge is meant to be used with compressor pumping- otherwise you are only measuring static pressure and need to ignore the red, yellow, green zones...

I bought a gauge kit, went to hook it up and noticed that the high side schrader valve is too small for the gauge to screw onto. So I just hooked up the low side. I had to clear the code from the computer and then the compressor would kick on for a few seconds and then back off and on again. Looking at the gauge, it would drop down to 20 psi and then the compressor would shut off, so I assume it still needs more refridgerant. So I had to order some more, I'm using Enviro-safe R12/R134a substitute that I got on ebay. I also ordered a can tap and an adaptor for the high side valve to use with the gauge.

Also I was measuring from the low side with the old gauge

sounds like for your safety and to protect the car's a/c system,you should stop working on it ,and see a professional,
( Man can move mountains but first must get the right tools and directions)

gransport3800 wrote:I bought a gauge kit, went to hook it up and noticed that the high side schrader valve is too small for the gauge to screw onto. So I just hooked up the low side. I had to clear the code from the computer and then the compressor would kick on for a few seconds and then back off and on again. Looking at the gauge, it would drop down to 20 psi and then the compressor would shut off, so I assume it still needs more refridgerant. So I had to order some more, I'm using Enviro-safe R12/R134a substitute that I got on ebay. I also ordered a can tap and an adaptor for the high side valve to use with the gauge.

Also I was measuring from the low side with the old gauge

What you filled your system with is basically a blend of propane and butane. I hope there aren't any sparks near the leak...

The code 66 mechanism is to prevent damage from the compressor continuing to short-cycle before the car is serviced. You need to clear the code from the computer before it will let the compressor run again. Disconnecting the battery for several seconds with the key off should work.

If the shrader valve pin is recessed in the high side port you will need the special "GM deep throat" adapter to connect to it. If the valve pin is level with the edge of the flare like the low side is, an ordinary adapter will work.

Leaks of HC (hydrocarbon) refrigerant can be detected with a common flammable gas detector.

I've read that those HC refrigerants were illegal in the states. Peoples houses have burned down when the car was left in the garage and that stuff leaked out.

Why not just spend the cash and get some r12?