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compressor locks up

Jim Davis on Fri October 03, 2008 8:48 PM User is offline

Year: 1989
Make: Chevrolet
Model: K1500
Engine Size: 5.7
Refrigerant Type: 134A
Ambient Temp: any
Country of Origin: United States

Just joined the forum, been looking, lots of good info.
Working on the above truck, was run for a long time with bad compressor, or so I was told, converted to 134, new compressor, new condenser, flushed thoroughly, dryer. . This same thing has happened with 2 other compressors, both rebuilds and I got it, put new compressor on but with all of them, it would/will run for a while, then the compressor starts to lock up intermittently, just once every few moments, then almost like clockwork every few seconds.

The owner and others who worked on it just thought it was a couple bad rebuilds, but its the same with this new AC Delco compressor. Pressures are fine, I forgot to write them down, and pressures do not seem to fluctuate when it locks. Any ideas welcome. This has me baffled.

GM Tech on Fri October 03, 2008 9:36 PM User is offline

You sure the compressor is locking?- or just can't turn once the head pressure raises- like in a loose belt scenario- Is the compressor seized when you shut the engine off- and you can not turn it by hand?

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Chick on Fri October 03, 2008 9:53 PM User is offlineView users profile

Just to add, is this being flushed without removing the O tube? If you remove the O tube, what does it look like? Clean or clogged, semi clogged, oil dirty after if locks up? belt wobbly??
Pressures are important, please post them when you get them...

Email: Chick


Freedoms just another word for nothing left to lose

Jim Davis on Sun October 05, 2008 6:33 PM User is offline

Sorry didnt get back, had some other things come up.
pressures: High 199-220
Low 26

The truck will idle and cool great, once you give it some rpm, after a few seconds the voltage to the clutch will begin to drop in and out, i thought the compressor was locking, it was doing it so violently, even a few sparks out of the clutch, looked for a relay, so far havent found one for the ac.

This is a new compressor, flushed system, new condensor, new dryer, new orifice tube.

mk378 on Sun October 05, 2008 6:40 PM User is offline

It's probably a bad cycling switch on the accumulator. Unplug it and jumper the plug, see if the compressor runs steady. If it does, change the switch (evaporator will eventually freeze without it). The switch has a valve under it so you can simply unscrew it and change it with the system still charged.

Jim Davis on Sun October 05, 2008 7:40 PM User is offline

Thats one of the two things i left out, sorry about that. I had replaced that switch, with an AirSelect brand 36664 SW 2647C Switch. Also when i put in the new compressor, on the old one the pressure switch on the back of it was the old one wire, and it was broken, replaced with a 2 wire from the gm dealer. Jumpered the switch like you said, it ran fine, cooled good, guess I will have to track down a different switch. Sure would help if i add all the right info, huh?

Jim Davis on Sun October 05, 2008 11:12 PM User is offline

I did find the relays for the ac, behind the glove box. The switch I replaced on the dryer was a number 36664, doing some searching, for a 4 seasons number thats for an R12 system, one for 134a is a number 36675. Guess thats my next step.

Jim Davis on Wed October 08, 2008 1:53 AM User is offline

Got the new switch, Four Seasons number 36675 and the problem seems to be solved, thanks for you guys help.

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