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I'll try to keep this brief. Went all last summer without a/c. Had a mechanic friend try to pump in some refrigerant, but it appears the system already has some in it.

The ECC blinks error codes. Checked the codes using the procedure in the techinfo here, and it keeps giving code 66, low freon. Clear the code, start the engine, attach can of 134, and the compressor kicks on and off about 5 times, then quits. Repeat about 4-5 times till i get sick of this process. Pressure gauge on the can is showing pressure in the system. My friend thinks the low pressure sensor/switch has gone faulty.

Has anyone else experienced this? Can one of those switches go bad? I looked on rockauto, and can't seem to find a replacement part of that.

Low freon codes typically clear and are common about once a year on some Bonnevilles. Not sure about your PA. I get that code once or twice a year on my 93 SSEi, I clear it, and it blows ice cold until the next time the code pops up. Others here are the same.

Was your system properly converted to 134A, or did you just add some to the existing R12 the car came with?

There is a sticker under the hood that says it was retrofitted, and has a time and date, and IIRC a shop name. It was there when I got the car

Have you cleared the code?

What pressure is the gauge showing on the can when it shuts off? Did the mechanic friend put the full gauge set on it?

A clogged orifice tube will cause a low low pressure reading, and a high high pressure reading. If all you are using is just a gauge for the low side on a can, this would fit the symptoms perfectly. No more adding refridgerant until you see what everything is doing.

Also remember an A/C gauge set is about $50. Well worth it IMO if you know what you are looking at.

Cleared the code, and it came RIGHT back.

The only gauge I have is the one on top of the can. It's showing in the 40's on the low side

What pressure does the compressor shut off at? Mine shuts off around 20psi. If yours is not doing the same, I would agree with you, sounds like a low side pressure switch issue.

I'm not sure, I haven't been able to get it to kick on in a while

I would try pulling the wiring connector from the low pressure switch and shorting the 2 wires with a cotter pin or similar device. Then see if the A/C works. I have used this method on the 99-07 Crown Vic Police Interceptors that I work on, and if the A/C works again, the low pressure switch is faulty. Maybe someone else can confirm/deny my diagnostic process? It may be a bit "redneck", and may not apply to your car. Don't try it until my method is confirmed.

renchjeep wrote:I would try pulling the wiring connector from the low pressure switch and shorting the 2 wires with a cotter pin or similar device. Then see if the A/C works. I have used this method on the 99-07 Crown Vic Police Interceptors that I work on, and if the A/C works again, the low pressure switch is faulty. Maybe someone else can confirm/deny my diagnostic process? It may be a bit "redneck", and may not apply to your car. Don't try it until my method is confirmed.

Readneck? Perhaps. Will it work? Yes. Should you watch the pressure gauge like a hawk when you do it? Oh yes, yes you must. You could also reset the computer by disconnecting the battery for a few minutes and reconnecting it.

Also, I want to confirm, you are checking the pressure while the compressor is running correct? Or was the 40 psi reading at rest?

RJolly87 wrote: Also, I want to confirm, you are checking the pressure while the compressor is running correct? Or was the 40 psi reading at rest?

The compressor won't kick on anymore. I tried the redneck fix. I'm not certain if I made a solid connection or not, but it did nothing. This weekend, if i get time, I will try to disconnect the battery so the electronics will reset. Maybe the ECC unit is crapping/freaking out

Today I disconnected the battery to let the electronics reset. The compressor then started doing the same thing as before, kicking on and off 5-6 times, then stopping. I hooked up the gauge, and it showed high pressure (like 60s), then it would drop to the 20s when the compressor kicked on, and back up when the compressor shut off. I cleared the codes once or twice, and tried again, and had no luck.

Now it went back to how it was. The ECC won't clear code 66, and won't turn on the A/C at all, even after I rigged the low-pressure shut-off switch with a wire. Baffled.

ECC unit taking a dump?

Nope, the system is working exactly as it should. It sounds like the system is low on refrigerant. The computer sees that low pressure switch is getting tripped very quickly, and very often, and then disables the system. Have the system properly evacuated, properly charged, and also have them put some dye in the system as well. Do not fiddle with attempting to bypass the switches any longer.

If it's low on refrigerant overall, wouldn't hooking up the can and recharging it fix that?

The can has lower pressure than the system w/o the compressor being on, so the system will actually try to back-feed into the can. I agree with randy.

Also remember that with only the low side pressure reading, you are only getting half the story on the A/C system. Another issue that would duplicate these symptoms would be a clogged orifice tube, or a bad or plugged expansion valve. If you try and add more refrigerant with this issue, you will only make it worse, because then you will begin tripping the overpressure switch.

Crap. Taking it in to a shop was my last resort. 2 summers ago i had a bad experience with this. Oh well, thanks for the help

That would be the best thing. The reason I say that, is because if you don't know what you are doing, it is really easy to screw up. Once you understand the concept, and the basics behind it, it is relatively easy to understand, but is something not easily understood by explaining through a forum.

I may be exposing the subject some here in a while as I have 2 vehicles that need attention in the A/C department.

I feel invincible in fixing cars. 2 summers ago when i had my bonneville, i paid a shop to fix the a/c at the price of $371, and it broke like a month later. So i bought some r-134 and fixed it myself for under $40 and it worked perfectly. That's kinda why I'm skeptical, but this seems more complicated. Also, in WI, you need a license to buy and service refrigerant and a/c systems. I would never break the law; but if i did, I would have driven to Illinois and bought a few cans of r-134