Automotive Air Conditioning Information Forum

Hello,
I have a somewhat unusual situation. My TJ 4.0L came with no AC but I checked out the situation and the wiring harness and engine accessory mounts are the same with/without AC so I bought every piece to install the system. All parts came from online retailers with reasonable reputations but low prices i.e. not exactly OEM quality. The compressor is a copy of SL7H15. I have good AC experience and have a vacuum pump, recovery system, gauge set, scale, valve tools, etc., and have done several repair jobs with good success.
So I installed everything, added 8 oz of PAG 46 (compressor was empty but came with oil in a bottle), and evacuated the system. The first time it didn't hold and I found a torn o-ring. The second time it held vacuum so I charged with 20 oz of R134a. The compressor cycled as I added refrigerant and stopped cycling as I approached the 20 oz charge. Everything seems in order except that the vent temperature was only 55F.
With the correct charge at 75F ambient, engine at 1500 RPM, the low side is 34 PSI and the high side is 325 PSI. By my understanding, this is very high on the high side.
So I am thinking restriction. The orifice tube is in the "liquid line" about 12 inches after the condenser and is not removable from the assemly. The line is very cold after the orifice tube but that could be normal. I wanted to consult with the experts before taking action. Again, every part is brand new but could possibly have quality issues.
The system has been working this way for a few weeks and is much better than nothing but I know it can be colder. The Jeep has only been driven once with the new AC.
Thoughts? More information needed?

With a high side of 325 PSI, my first thought is a condensing problem. At an ambient of 75 degrees, your high side should be no higher than about 190 PSI.

Are the fans working? Are all the shrouds and baffles in place? Are there any foam air seals installed to close the gap between the condenser and radiator? Are there any drastic temperature differences from one side of the condenser to the other, or top to bottom? Have you tried misting the condenser with water while watching the high-side pressure?

Thank you for your excellent insight. The fan is an old-fashioned engine-driven clutch fan and that 24-year-old clutch could be shot.

I didn't do any extra air sealing between the radiator and condenser and radiator shroud. I will investigate the sealing there and it probably needs improvement.

Great tip about the water misting - I will try that ASAP. I will also shoot some temperatures around the condenser - it's right up front with easy access on a Jeep.

Thanks again and I will report back with my findings.

twilliam wrote: ↑Sun Aug 15, 2021 9:00 pm The fan is an old-fashioned engine-driven clutch fan and that 24-year-old clutch could be shot.

Definitely. Those viscous-drive clutch units can appear to be working, but yours probably isn't up to the task of moving air through the condenser effectively, especially at idle. I would replace it first thing.

twilliam wrote: ↑Sun Aug 15, 2021 9:00 pm I didn't do any extra air sealing between the radiator and condenser and radiator shroud. I will investigate the sealing there and it probably needs improvement.

Without any seals, air can and will move around the condenser instead of through it as we would want.

twilliam wrote: ↑Sun Aug 15, 2021 9:00 pm Great tip about the water misting - I will try that ASAP. I will also shoot some temperatures around the condenser - it's right up front with easy access on a Jeep.

While misting the condenser, the high pressure should drop, indicating insufficient airflow. If you find any hot and cold spots on the condenser surface, they would indicate some sort of internal restriction.

Did you install a Recirculation door with actuator?

Tim wrote: ↑Mon Aug 16, 2021 9:39 am Did you install a Recirculation door with actuator?

Yes, I bought a complete AC airbox with actuators and replaced the old evaporator before swapping the airboxes. I also bought the dash control with AC positions.

Lucky junkyard finds.