01 XJ A/C issues

[87baseomatic]

Hello all, trying to figure out what’s up with the air conditioning on my father’s 01 XJ. Quick background, he’s owned the truck since 2004, has 170K on it now. I installed a reman compressor roughly 70K miles ago. I replaced the condenser about a decade ago due to an accident with a deer. Back in 2021 I vacuumed the system and refilled it using a robinair recovery machine at the vw dealership I was wrenching for at the time and the a/c worked fine. I believe the system calls for 20oz and I had recovered 17oz. Now that is getting hot in NJ, the a/c is acting up. The compressor clutch is short cycling, the FSM says low charge. I injected dye into the system, jumped the compressor and ran it then check with my UV light. Could not find any leaks, for arguments purpose, maybe it is low, I added 6 ounces of R134 to the system. Right now I don’t have access to an air con recovery machine so I can’t get an accurate reading on exactly how much refrigerant is in the system.

So I hooked up my a/c manifold gauges, with the engine running and the compressor clutch not engaged, I am seeing 38 psi on the low side and 40 psi on the high side. The clutch is still short cycling so I can’t get an accurate reading with the clutch engaged as it was engaging and disengaging every 5 or so seconds.

I bypassed/jumped the low pressure switch to get the clutch to stay engaged for long enough to get accurate readings. With the clutch engaged my low side is dropping all the way down to 5 psi and my high side is only reaching 125 psi, warm air is still blowing out the vents and the a/c lines aren’t getting hot or cold, electric fan never comes on either.

I’m a little stumped on what the issue is. I’m thinking either a clogged orifice tube or possibly a blockage in the system. The low side shouldn’t get that low. I’ve seen cars with weak compressors that are low on the high side pressure but still blow out cold air. The later 00-01 systems don’t have expansion valves so that rules out that being the issue.

Any ideas fellow Naxja folks?

 

[Saudade]

Sounds like you're still low. While r-134a systems are filled by weight, you can still use the pressures for diagnosis. With the compressor disengaged, and given enough time to equalize, the low and high sides should read about the same. Yours does. A "rule of thumb", that pressure would be numerically about ambient temp.

Even when you bypassed the switches the high side only got to 125psi. This is still too low. According to the FSM:

Low pressure at 80 deg 32-41 psi
High Pressure at 80 deg 200-260psi
Outlet temp dash center panel 33-44F

Of course these values will change based on ambient temps. This just provides a data point for comparison to your readings above.

 

[dktool]

Yep, low charge. 35 is a good minimum on the low side to shoot for without being able to correctly weigh in a charge.

 

[mpro1]

I'm having trouble getting my 1990 a/c system quite right as well. The entire system has been replaced with r134A compatible components; condenser, evap, reciever/drier, valve, compressor and all lines/ o- rings. Holds vacuum all day long no leaks.

There is 30 Oz of r134a in the system (80% of the r12 capacity)
Pressure is 32 low and 200 high @ 75°F

Problem will not blow below 50° F ?
Problem a growl/vibration/humming from compressor at low rpm.?

I come to believe the problem is volume of coolant related or air entering the system during fill??

Any advise or insight what is causing this would be greatly appreciated.

 

[87baseomatic]

Just to update the thread, it appears it was just low on charge. I put the rest of the 12oz can I had in the system, so the charge is somewhere between 12oz and 16oz now, based on what I know I’ve put into the system. It’s still lower than spec but the system is working.

At idle I am getting 60 degree air blowing out of the vents and the clutch is working as it normally should, it’s no longer short cycling. I am seeing 31psi on the low side and 290psi on the high side with the clutch engaged. That is before the electric fan kicks on. Mind you it is 91 degrees outside with 55% humidity here in NJ where I am working on it and the vehicle was stationary at idle with no additional airflow, nor did I hose down the condenser with water either. Oh and it’s a black XJ parked in the sun with no shade. Not the most optimal conditions, but based off various charts and the conditions, I’d say the system is now working in spec. Thanks for the responses.

 

[Saudade]

Still a bit low. FSM says 20oz R-134a.

@90 F: Low side 38-47 PSI, High side 250-300 PSI. Sitting in the hot sun, no shade could make the pressures a bit higher than in the shade since everything is still heat soaked.

I'd run it a few days and check again in the early morning/late evening if the temp drops or you can park in the shade.

Well done.

 

[87baseomatic]

Agreed, the low side is still below spec and the high sigh is showing on the higher side of being in spec but I suspect that is because of the conditions. I bet the high side will be substantially lower if I check it at nighttime when the humidity drops and the temperature drops down from low 90s to low 80s.

I have to get another can of R134 still as well. But in the mean time my father is driving it and using the a/c as it’s his rig anyway. When the sun goes down later and it cools off I will recheck the numbers and also check for leaks again. I can see the dye much better with my UV light at nighttime then in broad daylight anyway. I have a feeling the high side schrader valve is leaking slightly.