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Old 08-24-2019, 05:38 PM
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A/C Clutch Stays Engaged After Rebuild

2006 TJL Rubicon. Was sitting for 5 years before i purchased last year and I've been "renovating" ever since. I'm focused on the A/C but running out of summer. Here is what I've done so far:
- Ran Dye thru the system and identified bad compressor seals
- Compressed air test revealed leaks in the high pressure port & high pressure switch schraders. Also had an O-ring failure on the low pressure switch. Replaced all the schraders and O-rings throughout the system
- Replaced the compressor, dryer and orifice tube. Added 5 oz of PAG46 after shooting compressed air thru the condenser
- Vacuumed down the system - held a vacuum for 45 minutes
- Hooked up 134a 12oz can on a 82F degree day

Here is where I'm getting stuck. 1st half of the 134a can went in flawless, with the clutch cycling on and off, sucking in the contents. Toward the end of the can, they system STOPPED cycling. It stayed engaged. Pressures went to 65PSI low side and 235 PSI high side. Both were steady, but with the clutch engaged, i could hear the compressor start to whine. Cut the ignition to save the compressor. Tried a new low pressure switch and the same issue. Know I'm low on refrigerant, but think the system continue to cycle?

I'm having fun with the mystery, but looking for pointers on where i can look next (high pressure switch, ecm?). Thanks for the help.

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Old 08-26-2019, 08:54 AM   #2
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The low pressure switch cycles between 25PSI and 45PSI, since the low side is 65PSI that is why the compressor is staying on. If you only put ~12oz of R-134a in that system then, like you stated, you are low charge and it should be cycling as it sucks down the low side. What is the static charge (A/C off)?
But it really sounds like to much refrigerant is flowing thru the evaporator meaning something with the orifice tube is bad, o-ring maybe?
A slipping belt and bad compressor can also cause the issue you are seeing.

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Old 08-26-2019, 09:10 AM   #3
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Possibly way too much oil?
Did you drain all components before adding?

If the system was open for an extended time, 45 minutes may not have been long enough to boil off water...

How's your fan clutch? Lack of condenser flow causes high temps.
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Old 08-31-2019, 11:49 AM
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Thanks for the responses. It gets my brain working a bit. Let me bare my stupidity to help the diagnosis.
- When I say “rebuild”, I did the compressor, dryer, orifice tube, schraders and all the o-rings. What I DIDN’T replace was the condenser because I cheaped out. I also ran compressed air thru the condenser, which now I hear is heresy. Green oil and some debris came out the discharge side. Old orifice also had some debris on the screen. BUT my head figures compressed air was flowing so the condenser must be fine.
- the new compressor shipped with some oil inside, about an ounce. I drained completely but refilled with that same oil and additional PAG46 (thinking the compressor remanufacturer would only fill with PAG). The oil seemed different but I rushed and put in anyway. As an example, In the measuring cup, the compressor oil floated to the top and Appeared many shades darker. Read thru their instructions online (not provided) and did note to drain that oil before filling with PAG46. 🙄
- When I originally ran dye thru the system to assess why the AC didn’t work, the compressor seals were completely shot. I’m thinking now a blockage caused it to fail originally.

Now, I’m almost positive the condenser is slightly clogged, allowing the low pressure to build above 25 to start the clutch, but since it can’t move the 134a thru the system efficiently, pressure can’t build high enough on the low side to cycle. Hence compressor stays on. My gauge readings are static 45 low and 210 high (picture attached). Rest pressure is ambient temperature on high and low. Reason it cycles a few times at start is the 134a is equalized thru the system when off, creating enough pressure at the low pressure switch to cycle. Last owner probably filled the AC, got the compressor to kick on, but never noticed it not cycling. Finally it exploded from oil and refrigerant starvation.

Is my theory sounding right? I’m a bit nervous to test for blockage (with a laser temp gauge?) as to not damage further or blow up the compressor.

My approach will be:
- Evacuate old refrigerant.
- Replace old Condenser
- Drain compressor oil completely
- Add new PAG46, but how much??????? 6oz for the whole system but I have no clue how much is in the remaining components.
- Vacuum
- add 20oz refrigerant
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Old 08-31-2019, 12:59 PM   #5
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If you had debris then you really need to change out everything...
The system is contaminated with trash and now your new parts are also contaminated.

Running the compressor will not build pressure on the low side as that is the suction side. That would be no reason for the system to cycle unless the ambient temperature was low enough for the low side to get down to the point where it may start to ice up. If it's hot outside then system can run continuously.
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Old 08-31-2019, 01:05 PM   #6
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Btw 45 and 210 are normal pressures for about 80* ambient temp
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Old 09-02-2019, 03:50 PM
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Appreciate the feedback.

1) They are normal pressures (45/210) yes...but the system will cycle 4 or 5 times at start, slow steadily to where the low side cant build quite to 45PSI then abruptly stops cycling. Just stays static at that pressure reading (oscillating quickly between 210 and 212 on the high pressure side, like its struggling). Why would it stop cycling??? Even on the hottest days, compressor should make enough pressure to cycle the system if its orifice tube type. Constant "on" compressor just doesn't seem right.

2) FWIW I found the junk at the orifice tube before i changed everything out (except condenser). Shot air thru the system to remove all of it. But i still think the condenser may be junk, rotted from being open all those years......

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