Air Conditioning Does Not Switch On

...just a guess here - I believe if the Freon level is low, there is a safety device that prevents the compressor from running. So assuming there's no leak or failing component(s), the best case scenario would be a recharge.

"MG Midget >"

Thanks for pointing that out. It occurred to me as well that there might be some other sort of sensor involved.

But I was not aware that the compressor could be damaged if the refrigerant was absent or even low.

One day, I hope Saturn and other automakers just tell the driver in flashing signs on the instrument panel: "Bad Relay---Replace" or "Refrigerant Low or Missing----Re-charge the system!"

I'd guess it's low on refrigerant. (it's not freon)

fyi - Freon is a trade name for a family of chlorofluorocarbons from R11 to R227ea. It's usually used as a refrigerant. R12 is the old stuff and R134a is the newer, nicer stuff most commonly used in vehicle HVAC (and I'd guess most home/commercial AC...)

#1. Refrigerant is not a lubricant. That's why there's oil being circulated with it. #2. It's not freon.

No, it's not a trade name. It is a long gone BRAND NAME trademarked by DUPONT.

Are the R#'s still valid (like if you went into a parts store and asked for a can of R134a) ?

Yes. 'Cept you won't buy R12. There is a substitute however.

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Well, everyone has an opinion, eh?

Well it's not really an opinion in this case. It's fact. If the refrigerant is low, then there is a leak. PERIOD. It's like a transmission, low fluid = leak. No other possibility.

Okay, then technically is it typical that all AC systems leak? And it's only when you have to recharge the system more than once a year (or insert the appropriate period here) is the leak considered a problem? Otherwise I'm confused. Because for years Sears and Goodyear would offer a AC service and add Freon as indicated and said it was normal over the course of time (I'm thinking years, not months) for the level to drop. When I had my compressor replaced on my 97LS2 because of the whine (suspect bearing), they said it was low on Freon too and the rest of the system was fine.

transmission,

No, not all systems leak. I've checked systems that haven't been touched in

15 years to find them ok. I myself have a '94 SL1 that has never been added to or serviced. Some leak, some don't. If it's low, it has a repairable leak. Period.

Oh, BTW, it's not freon.

There are several conditions where the compressor will shut down:

Low refrigerant pressure - not enough volume of refrigerant. When suction side pressure is too low, the evaporator will ice up solid!

Low ambient temperature - there is usually some temperature sensor that will cut out the compressor in very cold weather to prevent damage to it. In cold weather, the refrigerant may not vaporize in the evaporator (cold weather defrost). Liquid refrigerant flowing back into the compressor dilutes the oil and can damage the bearings/bore. can also fluid lock the piston.

High pressure cutout. High side of compressor pressure is too high. This one is unlikely as the compressor would come on for a few seconds and then shut off.

Best thing to do is to check (have someone check) the low side pressure. I haven't worked on the new HC134A systems, only the old R12 systems. With the compressor off, there should be something like 50 psi (iirc).

Oppie

My understanding is that the old stuff is freon(R12) while the new stuff is not freon, but rather R134a. And yes you can get a can of R134a but not R12.

So what's in a 97SL2, R134a? (just curious)

I think it would be cool if you could run the AC a half hour before you get into the car without having to light the motor off - would be great in the summer, eh? I think I've seen a science mag doing something with solar panels and peltier (sp?) devices...

On my '89 minivan, the suction side hose developed a leak and lost all the Freon (R12). I replaced the hose along with a new H-valve (temperature controlled expansion valve) and receiver dryer. Accounted for all lubricating oil in the parts removed and pumped down. Since I never bothered to get an EPA license to handle refrigerants, I had a friend refill the system with FR12

the same properties as R12 and compatible with the oils used inthose systems (mineral oils). Worked great and at a fraction of the cost ofR12.

Oppie

Even most of the r-12 was not freon. Freon is a brand name.