My compressor clutch engages constantly

Lee · Mar 30, 2015

I replaced my ac compressor, accumulator & orfice tube last fall when the ac compressor went out.

I flushed the system, put it on a vaccum & charged the system, everything worked fine but I did notice the compressor clutch would engage about every 30 seconds.

Everything worked fine til last week the ac compressor went out again (cheap chinese garbage)

Flush, replace compressor, accumulator, & orfice tube, vaccum system, charge the system.

Everything works again, but the dang copressor clutch keeps engaging every 30 seconds.

Now at an idle when the cutch engages it almost stalls out the engine, I had to start shutting off the ac when I came to a stop light/sign or else I would nearly stall out when taking off (5 speed manual)

Could it just be the cheap rebuilt compressor causing all the trouble or is it an electrical issue?

Thanks Lee

RonD · Mar 31, 2015

The compressor is on with the A/C of course but also when Defrost is on.

If it is cycling when A/C is on then could be pressure in the system is incorrect, compressor clutch is activated via 2 pressure switches, if either "opens" then compressor stops until pressure goes down or comes up and the switch closes again.
If you are just using cans of refrigerant without gauges then that may be the problem.
And going thru two compressors in a short time could be "cheap equipment", or may indicate a problem in the system.
IMO, it may be worth having A/C serviced at a shop.

Computer should open IAC(idle air control) valve more, to increase idle, when A/C compressor comes on, it reads like this is not happening.

The wiring for the '96 4.0l compressor goes like this

Heat Control switch(12v)------(clutch cycling pressure switch)-----(AC pressure cutoff switch)-----(splice)-----(WOT Relay)-------(compressor clutch)------Ground

The (splice) also goes to pin41 on the computer, if this pin sees 12volts computer should increase idle.

The WOT(wide open throttle) Relay is controlled by the computer, it does what it's name implies, if you floor the gas pedal to pass or to go up a hill the computer will shut off power to the compressor so you get full engine power.
The relay's coil gets power when key is on, but the computer controls coils Ground, pin69, this allows computer turn off compressor.
Never heard of a WOT relay going bad, but it could, it is in the engine fuse box, it is a standard Ford relay.
If you start the engine and turn on the AC, then open the fuse box and put your finger on the WOT Relay you should be able to feel it click open or closed with the compressor's ON/OFF if this relay is causing the issue, if compressor is still cycling on and off but WOT relay is not "clicking" then that is not the problem.

kimcrwbr1 · Mar 31, 2015

Did you charge the system by weight? It dont take much to overcharge a system and could be why the first new compressor went bad. If the compressor is slugging liquid refrigerant say goodby to that compressor. A set of guages will tell you whats going on with the system as it cycles. Did you add compressor oil?
https://www.rtitech.com/downloads/News/Oil Chart - Compressor.pdf

Lee · Mar 31, 2015

I forgot to mention that I replaced the low side pressure switch when I replaced the compressor the first time, maybe I got a bad switch?? I hung on to the old switch I'll try swapping them out & see if that makes a difference.

I did buy a set of gauges & a vacuum pump in order to replace all the parts last time.

Yes I did add 7 oz of PAG46 oil half in the compressor & half in the accumulator. I turned the compressor clutch with a spanner wrench to cycle the oil throughout the compressor & after it was mounted & all the lines were hooked back up I turned the clutch with the spanner wrench a dozen times to pump out the excess oil.

Per the sticker under the hood I added 1lbs. 9oz. Or 25oz

The first time I recharged the system I added 2 12oz cans & I had a left over can with tiny amount in it. this time I had 2 18oz cans I added 1 can & then added not quite half of the second can, keeping an eye on the gauges the whole time, pressures on either side never got to high.

I'll hook up the gauges again tonight & post up the numbers

Lee

kimcrwbr1 · Mar 31, 2015

A single drop of water will gum up the works and water mixes pretty good with the POE oil.
They say to evacuate for at least 45 minutes but the longer the better as far as I am concerned. I like to blow out both coils good with nitrogen to remove the old oil and water just prior to closing it up. You need to pull it down below 300 microns vacuum pressure to remove the water from the oil. Car systems are so small 2hrs is usually good enough you cannot leave the pump on for too long!

My compressor clutch engages constantly

Lee

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RonD

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kimcrwbr1

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Lee

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