A/C compressor not cycling on

[1998_K1500_Sub]

What about a used compressor from a junkyard?

How do you know what's in it? I suppose if one pulled it themselves, and looked at the orifice tube screen first, one might assume it's not full of crap. But otherwise... open it up and check it out, look at the valve petals, see what's inside before putting it on, but that takes little skill and probably an O-ring kit.

It's a $$$ vs. risk tradeoff. I know not everyone can simply "spend the money".

 

[Nad_Yvalhosert]

How do you know what's in it? I suppose if one pulled it themselves, and looked at the orifice tube screen first, one might assume it's not full of crap. But otherwise... open it up and check it out, look at the valve petals, see what's inside before putting it on, but that takes little skill and probably an O-ring kit.

It's a $$$ vs. risk tradeoff. I know not everyone can simply "spend the money".

Partially right. Try to buy it from a working A/C vehicle, only take it if its physically clean.
That being said, getting a can of A/C flush is expected. Cleaning and washing pre installation. And that's what the 30 day warranty is for. Time to install and charge and see if it's good.
Get it, get it washed, get it PAG oiled, get it installed ASAP.
Then after 2 weeks you'll know and have time to return or swap out. It's still cheaper to try now, then it would be in July when its 100+° and there's a week of customer A/C work ahead of yours.

 

[1998_K1500_Sub]

a can of A/C flush is expected. Cleaning and washing pre installation.

Makes sense.

So when pulling vacuum, be sure to pull it long enough to vaporize any flush that would not drain from the compressor or otherwise remained resident in the compressor (I like to hold vacuum on the system overnight). And by the way, that flush will contaminate the vacuum pump oil and (if contaminated enough) prevent it from pulling full vacuum, so plan to drain / refill the pump oil after the first vacuum attempt. As me how I know.

I've smelled "flush" in the exhaust and oil of the vacuum pump at least once.

 

[Queso Del Rio]

Yes, you do know.

Spend the money, make the A/C work properly, long-term.

Your Grand-dad lived without A/C in his car...doesn't mean you have to.

Yup, I'd say replace everything for warranties and peace-of-mind. My Granddad used to put a couple of candles on the dash, go back inside and eat breakfast. He'd go back out and the truck would be warm and the windshield would be defrosted. Of course, the windows were the A/C back then too. A/C repair places would get more work if vehicles nowadays didn't turn the compressor on when you hit defrost!

 

[Nad_Yvalhosert]

Of course, the windows were the A/C back then too.

You're referring to 2-70 A/C. 2 windows down, 70 MPH

 

[GMTMark]

A few years ago I bought a kit from Auto Zone with a little battery operated UV flashlight. I don't remember the exact price but it was very cheap and I still use it.

 

[Old man]

I just noticed today that my A/C ‘94 350 is blowing hot and compressor is not cycling on. It seemed to just stop blowing cold. After a little research I tried bypassing the cycling switch with a jumper and compressor kicked in. Thought it was the cycling switch so bought a new one and same problem. Is there anything else that controls the compressor engage? Can low Freon cause it not to cycle? Should it cycle no matter what? Is there a chance the new one is bad too? Replaced with GM part The A/C was rebuilt about 4 years ago.

Thanks for your time!!
Kevin

Did you check the relay? If freon is low it wont allow compressor to work check that first. I would swap the relays blower motor ac compressor fuel pump should all be the same

 

[Schurkey]

Did you check the relay? If freon is low it wont allow compressor to work check that first. I would swap the relays blower motor ac compressor fuel pump should all be the same

He jumpered the low-pressure switch, and the compressor worked. That verifies everything in the wiring system except the low-pressure switch, which he replaced and got the same results.

The system is under-charged.

The system is under-charged because the compressor leaks. We knew that in post #10.

 

[K-Man]

Umm... can you be more specific? "Blew Freon all over" might have been a sudden, possibly massive discharge. I can't imagine a compressor would do this unless it (a) popped a high-pressure protection orifice or (b) it pushed-out an O-ring or ruptured a line.

The point: What you're seeing may be due to some other factor, like a blockage in the high-pressure line (to name but one of many factors that might have lead to excessive high-side pressures).

Can you tell us something about the "debris field"? Can you pinpoint the source of the discharge? That will provide more insight into the root cause.

 

[K-Man]

Here are two pics in the dark with UV. The back of the compressor is clean.