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XJ A/C High Pressure Side too low, bad Condenser?


NAXJA Forum User
Hey all! Long time reader/first time poster, thanks for all the gems of knowledge posted on here! Been super helpful in my adventures fixing my XJ.

Recently got tired of my 2001 XJ blowing hot air all the time, and wanted to do an AC overhaul! The A/C clutch plate was super rusted out (discovered as I was going for the shim removal "mod") but would engage at times, and system would hold refrigerant, HOWEVER, the HI side was always much too low (less than 100PSI with the clutch engaged). I swapped out the compressor, dryer, and hi-pressure line with a set from UAC. I opted to not swap out the condenser, as the compressor didn't die so it shouldn't be tainted with metal bits, the system appeared to have no leaks, and I have a modded front bumper that's a pain to take off.

Fast forward to a successful install+vacuum+recharge, plus replacing the low+high side sensors/switches, my high pressure side is still too low @100PSI, and I need to overcharge the low side to 50PSI to get the clutch to engage at all (with A/C at max).

Since the low side the system is holding refrigerant and the compressor+dryer+sensors are brand new, is it possible I have a leak in the condenser causing this imbalance? Something I'm missing? I'm stumped!
I should add, when I charge the low side to spec (between 25-35PSI), the compressor simply won't kick on and the Hi pressure side stays around 50PSI.
How much refrigerant did you put in? R-134a systems are charged by weight, not by pressures. Pressures are used to diagnose problems. You sound like you're still undercharged.
Assuming the gauges are accurate, I think the compressor should still kick on at 35-psi. Odd that the high side says 50 when it's not running though. Bad or incorrect low pressure switch? What happens if you power the compressor directly? If the low side pressure drops immediately, I'd agree it's likely undercharged.
How many cans did you put in? How much do you know about recharging the system?

You add the freon through the low side, which will increase the pressure on the low side to above "normal" but the pressures should equalize. Compressor will not turn on if the whole system does not have enough pressure. Your system should take 20 ounces of r13a... I would vacuum the system back down and use a small scale and weigh the containers, this is the best way then using gauges.

I read you replaced the compressor, in the new compressor did you drain the oil that was in there, they load the compressor up full with oil for shipping and storage. Did you also measure how much oil came out from the old compressor?
*Cant find the edit button, I said pressures should equalize which isn't true... the pressure will find its way to the high side and the expansion valve should do its job regulating the pressure for the high and low sides...
When not running and allowed to stabilize, both side would read the same. It may take more than a few minutes to equalize after shutdown.

When charging, you close the high pressure side valve on the gauge so you charge through the low side. Assuming it held vacuum, the vacuum should draw in enough refrigerant for the compressor to kick on.

My FSM say 1.25 lbs is required. The 2001 uses a fixed orifice, not an expansion valve.
Thanks ya'll! Missed the forest for the trees on that one, didn't have enough refrigerant and was getting spooked adding too much to the low side. Allowed pressures to equalize and everything is operating perfectly! Much appreciated.

I did dump the oil from the compressor after shipping and refilled to spec (8.1oz IIRC), while turning the clutch by hand to ensure everything got lubricated before install.

Brings joy to my heart to see that Aux fan finally spinning :heart: