HELP R4 compressor not cycling runs constantly

69hurstolds

69hurstolds

Comic Book Super Hero
Jan 2, 2006
2,542
113
If it's overcharged, it won't cool as well as a correct charge. That "leaky gage" might have released some 134 and in doing so might have got you closer to a proper charge which begets colder vent temps, if it actually is overcharged.

I hate remote diagnostics. Can't see it can't do much with it. I suspect it was overcharged. Depending on outside temps, you should run around 25-30 ish on the low side and likely 150-200 ish on the high side. But again, outside temperature conditions make a difference. The hotter it is, the higher pressures.

If you have 35 psi on the low side, that may (emphasize MAY) be ok. IIRC, 45 is the upper limit of "normal". But if you were at 60 that's way too much. Try revving the engine to around 2000-2500 rpm and hold it and see if the compressor cycles. It may take a slight bit to see it doing it, but if it's properly charged it might. The main key is that there's no moisture in the system. That really can wreck your system trying to get it to cool right.
 
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hoffa65

Greasemonkey
Mar 11, 2019
232
43
Atlanta GA
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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Depending how long after you ran the AC before you connected the gauge the pressure will change.
At rest the charge psi will be approx equal to air temp. As the system runs the high side will increase and the low side will decrease until they get to there normal working pressures.
Need some background on the system. When was it put together was it evacuated before charging?, How long has it been since the system has had charged added?
Set the AC controls on normal and fan on high, let system run for 5-10 min and check low side reading. If you have a thermometer put it in the center vent, you should get a 10-15 degree temperature drop from ambient air temp with the low side running around 35 psi.
If so put AC controls on max with windows up let run another 5-10 mins. Lows side pl ressure should slowly come down as cabin temp drops and compressor should cycle when pressure get to 28 psi
 
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Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
362
43
Tampa Bay Area
Depending how long after you ran the AC before you connected the gauge the pressure will change.
At rest the charge psi will be approx equal to air temp. As the system runs the high side will increase and the low side will decrease until they get to there normal working pressures.
Need some background on the system. When was it put together was it evacuated before charging?, How long has it been since the system has had charged added?
Set the AC controls on normal and fan on high, let system run for 5-10 min and check low side reading. If you have a thermometer put it in the center vent, you should get a 10-15 degree temperature drop from ambient air temp with the low side running around 35 psi.
If so put AC controls on max with windows up let run another 5-10 mins. Lows side pl ressure should slowly come down as cabin temp drops and compressor should cycle when pressure get to 28 psi
Thanks I’ll do that I’m not positive but I wanna say the ambient temp was between 87-90 degrees. I let the car warm to operating temp with the ac running max the whole time. So I believe the ac was idling at max for more than 10 min and the gauge was reading 55 or 60 I think on the low side. It hadn’t once disengaged the clutch so I unplugged the low pressure switch real quick to see what it did and the gauge jumped way up to like 80 psi or something.

Then the leak happened and the idle psi was around 35.

System was charged last I believe a year ago however for part of that year it wasn’t ran because of belt issues. A shop did it for my dad after we replaced all the components and made the system sealed. I assume vacuuming the system down would have removed the moisture and I mean I would hope the shop vacuumed it down well.


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Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
362
43
Tampa Bay Area


Ambient temp of 94 not counting humidity. Ac on max blower on max full operating temp.

Also static pressure is about 110

Did not move off that pressure at all didn’t raise or lower.

However system pressure shoots way up if the compressor clutch is disengaged.

Compressor didn’t cycle at all even at 2500 rpms




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oldsmobile joe

Royal Smart Person
Nov 12, 2015
1,014
113
mpls
Looks almost normal for your location. If you were to spray water on the condenser, what happens? If the pressures drop, then you may have insufficient air flow across it and the radiator. Then i would look between the condenser and radiator and see if you have build up on the fins.if no build up on the fins, i would look at the cooling fan.
 
Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
362
43
Tampa Bay Area
Well I didn’t get a chance to spray any water but I know there is no build up because just a week or two ago I blew out the condenser and radiator with water and popped the radiator plate off the top to inspect and clean between them. As far as fan it’s a mechanical flex fan on a non thermal clutch.


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Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
6,256
113
Queens, NY
35psi is more normal. Of all my cars none cycle except the Jeep. The Jeep manual says cycling less than 10 times a minute is normal. But it actually does NOT cycle much unless the gas leaks out and gets low. A fresh vacuum down and refill with the CORRECT amount of 134a gets me around 30 psi at idle and up to 35 degrees below ambient temps. Overcharge gets me 20 degrees or less. I think you accidentally "fixed" it.
 
Stupidquestionspro

Stupidquestionspro

Master Mechanic
May 23, 2019
362
43
Tampa Bay Area
Yea from what I read 50psi on the low side seems normal for the ambient temp at the time I’m just surprised because I always thought the compressor would run for a bit reduce low side pressure then stop low side pressure would rise and the cycle starts all over again. All mine does is literally sit at 50 steady the whole time.

Also what are the symptoms of too much oil in the system?


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hoffa65

Greasemonkey
Mar 11, 2019
232
43
Atlanta GA
Looks a bit overcharged yet, high side should be 275-300 psi. Low side should pull down to 40-30 psi after cabin has cooled to 70-60 degrees.
 

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