HELP R4 compressor not cycling runs constantly

Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
361
43
Tampa Bay Area
I have the 1968 sbo 350 in an 83 Calais body the ac is all the more modern set up the compressor is an R4 with an accumulator and a low pressure switch on the accumulator. The ac works not great but it works but unless I manually unplug the low pressure switch or clutch plug or of course shut the a/c off entirely the clutch never disengages just runs constantly no matter how long the car is running.

I’m not super experienced with ac but I’ve never seen a compressor that doesn’t cycle at all. Would that be correct or is my Freon to low or too full what could cause it to be constantly engaged?


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olds307 and 403

olds307 and 403

Geezer
Oct 14, 2008
5,057
113
Melville,Saskatchewan
Mine was doing the same thing. If anything it would be over full.
 
Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
361
43
Tampa Bay Area
Ok cool thanks so there is only the low pressure switch on the accumulator and it running all the time wouldn’t mean the switch is bad right?


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O

oldsmobile joe

Royal Smart Person
Nov 12, 2015
1,044
113
mpls
You need to hook an a/c gauge up to it and read the low pressure and compare that reading to the switch spec.
The switch could be stuck, the system could be over charged, or, its just running normally.
 
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Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
361
43
Tampa Bay Area
Thanks so there are occasions of normal operation in which the clutch never cycles?


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H

hoffa65

Master Mechanic
Mar 11, 2019
274
63
Atlanta GA
Thanks so there are occasions of normal operation in which the clutch never cycles?


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Yes if it has the correct charge at idle it should not pull the low side down to cycle the LP switch and run constantly.
Now if the system is over overcharged it will run constantly and not cool well. Same if the system has moisture in it.
 
Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
361
43
Tampa Bay Area
Ok so the only pressure switch is that one low pressure switch. So if the switch isn’t bad and the system isn’t over charged then it’s working normally I don’t believe the compressor even cycles when accelerating it is literally running all the time and the accumulator and one ac hose puts off a lot of condensation and the other hose gets quite warm.


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H

hoffa65

Master Mechanic
Mar 11, 2019
274
63
Atlanta GA
Should cycle above 2k rpm.
Low side should sweat, and high side is normally qyute warn.
Really should put a gauge on it and check operating pressures if nothing else just on low side with a refill can with a gauge. Should be in green markings on gauge at idle and pull down to about 28 psi and cycle at 2k rpms
 
69hurstolds

69hurstolds

Comic Book Super Hero
Jan 2, 2006
2,613
113
A quick, free and easy test, pull the cycle switch socket and see if the compressor shuts off. Then reattach it and it should restart. Not proving the switch is bad or not, but it might tell you if you pull it and it doesn't shut off, you may have an issue with the clutch not releasing or a wiring issue.

Just a question- I'm assuming you did a 134 conversion from R12? If so, did you remember to do about 75%-80% (approx.) 134 to R12? If you put the same amount of 134 in it, then you're likely to be overcharged. Not accusing, just a question.

Obviously I agree with hoffa65 - stick some gages on it and see where you're at.
 
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Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
361
43
Tampa Bay Area
The low pressure switch when unplugged instantly unlocks the clutch so it seems to be working.

The can gauge on the low side mind you one of the cheap ones not true ac gauge showed 55 or 60 psi unfortunately it had a leak or something and ended up around 35 psi later and of course mind playing tricks I think the ac is colder now. Also it’s 134 in it. Though from what I can tell the compressor still isn’t cycling so who knows but in Florida better ac is always nice.


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