Automotive AC question

[billfish678]

Hi all.

Have a relative that has a problem with their automotive AC system. Looking at it for other reasons the other day I noticed one thing. It appeared that the clutch on the compressor was cycling on and off every few seconds. I suspect that would be due to the pressure in the system being borderline and the pressure switch shutting it off every time the pressure drops. Is that the likely problem?

Secondly, I have one of those el-cheapo AC refill kits. I've used it a few times with some luck. This particular vehicle is an American made 1999 model. Is that late enough that I can be sure that whatever the coolant of today is the coolant that was used back then?

Thanks!

[SanDiegoTim]

The clutch cycling issue could be electrical as its engagement is an electrical function. For example, when the starter motor is engaged, the compressor is not.

Can't help on the refill question.

[Gary T]

It's a virtual certainty that the rapid clutch cycling is due to low refrigerant (not coolant -- coolant is in the radiator). I've never seen it caused by anything else.

All 1994 and later vehicles use R-134a refrigerant.

[billfish678]

Yeah,

I meant refrigerant. So it sounds like I am on the mark with this one. Could this actually be one of those once in a lifetime easy fixes?

Thanks guys!

[Gary T]

Originally Posted by billfish678

Could this actually be one of those once in a lifetime easy fixes?

Yes*, so relish it appropriately. Of course, once you've experienced it, there's no particular reason for the universe to keep you alive.

*It may not be the complete fix, which could include finding and fixing the leak, but unless there's a big leak we'll call it the fix.

[blasto9000]

The A/C compressor clutch cycles on and off in normal operation. There is a temp sensor on the evaporator, so when it gets cold enough the compressor is temporarily turned off. As the warmer cabin air blows through the evaporator and warms it up, the compressor is switched back on to provide cooling. Depending on the conditions, the compressor may cycle on and off every few seconds.

If this is how your compressor is behaving, then the a/c loop is probably working. Possibly, the cooled air is not being routed through the ducts correctly.

[FoieGrasIsEvil]

OP I had a similar case with my Hyundai recently. I discovered not too long after purchasing it that the a/c didn't blow cold air, so a couple weeks ago, I resolved to buy a can of refrigerant and a hose to fill it, hoping that it would resolve the issue and that the "stop leak" type of refrigerant I bought would stop or slow down the leak that caused it to run out in the first place.

I noticed what you did as I was beginning to ready my fill job, as the instructions tell you to turn the engine on and run the a/c at max temp and fan setting. The clutch wasn't doing anything! But once I had added some of the refrigerant, it started doing its thing again, and for the last two weeks, I've had cold air. I also have no idea how long it will last!

Its worth it if it fixes it and if it doesn't because the leak is too large or there's something else wrong, you're not out a whole lot of money.