A/C compressor never kicks on

[shinobis]

Wanted to know other then changing the compressor would there be any reason why it would not kick in. The blowers work fine, and the belt actually looks new.

93Limited

 

[Redrig]

It maybe low on freon/r134

 

[shinobis]

Had a friend convert it, sucked up three cans of r134, and still nothing. He even said he said the gauge did not register any pressure

 

[Redrig]

Did it work prior to the conversion?

 

[shinobis]

As per my dad who bought the truck originally it did, but I suspect he was talking about the blowers

 

[Redrig]

I guess it is just shot. I really dont know a whole lot more about them, maybe someone has an idea. Goodluck

 

[Glacier991]

Before you assume it is shot, check system pressure. If it is over 40 psi, check to see if there is 12V at the clutch. If not, then try jumpering the low pressure cutout switch on the accumulator. If it runs then, you have a bad low pressure cutout switch (not uncommon). It is easily changed, and is on a schrader valve so you don't have to discharge the system to replace it. Let us know what you find. (btw 3 cans? A little much.)

 

[shinobis]

Supposedly there was no pressure at all. Also he filled it with the cans and he said he didnt hear anything coming out, but it took all three cans of the kit.

 

[Glacier991]

take it to an AC shop and let them put the gauge set on it. You can buy one for $50, but pay them $75 to diagnose it. I'm guessing a leak check, evacuation and recharge will fix you right up. (Good old Walmart kits...)

 

[shinobis]

Yes figured it would come to that. Will do

Thanks

 

[DMan446]

Yeah if it took all 3 cans and still showed no presure, it sounds like a bad leak. Also you have to make sure you fill the right side. There is a high side and low side connections. If you fill the wrong side its bad news.

It was mentioned to short the low pressure switch. This does work, but I would not recommend leaing it shorted any more than 5-10seconds tops. Cuz if you cut the compressor in with no freon in the system, it will burn up the compressor.

A shop will first check for pressure, if there is none(as the same reading you got) the will do a vacuum test on it to see if there is a leak in the system.

There is also a one-way orifice in the lines going through the firewall. The slightest amount of debris will plug this causing the system not to work.

But most of the time when you have to do a R12-R134 change over, some items need to be replaced first. Like the orifice and evaporator/collector tank.

Its real easy work, but when you dont know how to do it, they carge an arm and a leg for it. I worked at a shop that did ac work, so I have pretty good knowledge of how their tricks work.

 

[dmaster79]

I had similiar problems with my system, converted it and charged it, it holds pressure or so I assume, but the clutch would not engage on the compressor. There was no 12v getting to it, so I just ran a jumper wire to the hot side with a switch to engage the clutch manually. With a switch I can turn it on and off at any time. It seems to work, but is this a good idea or am I doing something harmful by bypassing the system?

 

[Glacier991]

Possibly. In a fixed orifice system the low pressure switch prevent evaporator freeze ups, and prevents running the comprssor "dry" and burning it up. I'd fix the switch an/or wiring.

 

[dmaster79]

Thanks for the reply glacier. I investigated a little more today and ran a tester on the line one more time and too my suprise it has juice now, so I hooked the wire back up the way it should be. I guess I forgot one important fact and came across this upon reading these forums, if the pressure is too low, the pump will never activate. Now I have the question, how frequently should a pump run. Mine kicks on for like 10 seconds, then kicks off for a few, however the ac still works, is this normal or am I still just too low on coolant. Thanks

 

[DMan446]

Its normal for it to cycle on and off.

 

[Glacier991]

yes it does cycle.. but very frequent cycling in warm weather can indicate a low refrigerant charge.