We just had sub-zero temps here in Maine and my truck took some icing. The AC compressor just stopped working. I need it to dry the air inside the cab when it warms up and starts melting all the snow on the floor boards. Otherwise the windows fog and then it actually freezes to the inside of the glass in places (yes, it was that f'ing cold). So I run the heater with the AC turned on so the air is run through the drier first.

What would cause the compressor to just stop working?

The AC light in the cab is on.
Fuse is good.
Belt is fine.
No obvious leaks.

If the freon gets low will that keep the compressor from kicking on?

Any other culprits anyone can think of.

Is this best trouble shot with a professional?

Thanks all.

 

Well, the major diagnostic step is to see if the compressor is turning or not by looking at the inside of the pulley. In either case, the next step is to hook up a set of gauges and see what the readings are both stopped and running. A/C work without a high and low gauge set is a waste of time. HarborFreight has a set for a good price that does the job for occasional use.

Some places will diagnose for free. AAMCO, I think?

Learning to do my own A/C work has required more study than any other DIY thing I do.

 

Low or high pressure switches if the system pressure gets to high or low it will shut off.

Just the cold temps might be enough to cause a poor connection at one of those switches

the clutch might not be pulling in due to being to cold grease to thick ice preventing it from moving

 

TheDurk and wyoming9,

Thanks for the replies. Thanks for the heads up on Harbor Freight as a venue for getting gear. I've heard the same thing that DIY AC work is in depth.

The mention of it actually being too cold I think was the problem. I cranked up this morning (~40 deg F) and the compressor kicked right in. Man it was cold before.

While I'm at it, what are the usual regular maintenance steps to be taken for an AC system? I'd like to keep it in top shape as best I can. Are there fluid changes, filter changes, etc. that can be performed?

Thanks again.

 

Not really much you can do but using it is better then just letting it sit.

seeing that it has the proper charge every spring is also good.

Washing the condenser off now and then does not hurt.



Been a few years since I was up in the Bangor area .

 

wyoming9,

Don't make the trip up here now. It's cold as a well digger's ass.

Is the condenser the "radiator" part? Do I just clean like I would a clogged radiator?

Thanks.

 

Our trucks run the A/C anytime you use defrost so you don't have to worry much about that--it gets used. Checking refrigerant levels in the Spring is something I do on all my cars that aren't brand new. Other than that, like Wy9 said, not much you can do until something fails. Checking belt tension in the Spring and cleaning the condenser with some compressed air or a garden hose are good things.

 

Thanks all for the lessons here. I've got AC plans for the Spring now. Until then...

 

Okay, so it seems the system has a low charge. When it's warm the freon expands and increases the pressure and the compressor will kick on because it is getting a high enough pressure signal. But when it's super cold the freon pressure is lowered enough to send a low signal and the pressure switch won't let the compressor kick on. Pretty damn cool!

So a recharge is in the near future.

Question: Do I need to add some kind of oil when I put a can of 134a in the system?

Can I do this when it's cold or should I wait until the outside temps are warmer?

Thanks all.

 

It has been a few years since I was in school so I might not be remembering correct.

You can recharge in colder temperatures but have to calculate pressures for that temperature.

If not as you have figured out you would be way over charged when it gets hot.

Like I said not real sure and don`t feel like digging up text books and my notes.

 

And you *probably* don't need to add oil. Many recharge kits sold in stores contain the oil, because it's somewhat safer to have to too much oil than not enough. But if you have a slow leak and keep adding cans with oil eventually the system will have too much oil in it and not enough refrigerant, and lose efficiency.

 

the extreme cold will also drop the pressure down..