ptaylor

Good Morning Cherokee!

Having an issue with my A/C system on my 2000 Jeep Cherokee 4.0/6cly. My A/C blows hot. Here's what I've done:

1) Mechanic evacuated the A/C system
2) Replaced compressor, accumulator(receiver/dryer thingy), condenser, high and low pressure aluminum/rubber tubes & hoses (connecting the compressor to condenser/accumulator
4) Mechanic installed compressor, added oil and recharged the system
5) Ran cold for 1 week or less
6) Ran a gauge on the low side for now (50psi) @ 85 deg F.

***Did NOT replace evaporator***

Also, does my model have an orifice tube, expansion valve, or both? I was under the impression that it was in the aluminum tube from the condenser to the evaporator

Any ideas? Thanks!

ZJMAX

Check that your blend door is switching to the ac side and not stuck on the heater.

Max

MoparNJeep

Replace the evaporator..

brian23456

+1 on the blender door, and I may be wrong but isn't 50 kinda high? I would have to go out and check but I think mines at 30-35@ 80° and it's running great, if I charge it to 40 it doesn't get as cold.

Rambler65

A fixed orifice tube is used in these systems, according to the service manual it's inside the liquid line at the condenser end.

The manual lists normal pressures as 200-260 psi on the high side, 32 to 41 psi low at an ambient temperature of 80 degrees.

You really need a full gauge set to see what's going on. Without high side readings you're working half blind. It is certainly worth checking the blend door though to make sure you're not getting reheated air from the heater core.

ptaylor

Thank you for your replies!!!!!!!!!!!!!!!!!!!!!!!!!

2000 Jeep Cherokee 4.0/6 cyl
All components are 2 years old minus the evaporator

I am new to A/C diagnosis obviously

Here's the situation that was happening to the A/C system during dual A/C manifold gauge diagnosis (92 deg F/Humidity > 75%):

1) Compressor cycles 8 times per minute (about 5-6 seconds the clutch engages and spins with accessory serpentine belt). Compressor makes a loud click noise when it stops. Compressor is a RockAuto reman that is 2 years old.

2) Low side rises to 55psi then compressor cycles to bring it down, then rises again immediately. Gauge needle consistently jumps on way down

3) High side rises to about 135psi then compressor cycles to bring it down to about 90psi, then rises again immediately. Gauge needle jumps intermittently on way down

4) Aluminum line from condenser to evaporator is sweating and very cold

5) Aluminum line from compressor to accumulator/receiver-dryer is hot or near ambient temperature

6) Cabin temperature is around 90 deg F blowing from middle 2 vents

7) Auxiliary cooling fan (adjacent to main radiator fan off engine) turned on 6 min

8) Static gauge pressure on A/C system matches ambient temperature (90ish on both high and low meters)


Again, any advice is greatly appreciated! Have a good one!!

Rambler65

The fast cycling would be consistent with low refrigerant charge, though there may be other conditions that would cause that symptom.

What are the pressures with the compressor engaged and engine running at fast idle, about 1500 RPM? (You can try briefly putting a jumper across the low pressure cutoff switch if needed.)

If low side is too high and high side too low it could be an indication of a compressor problem, but the pressures need to be verified with the compressor engaged.

ZJMAX

Again, Check the blend doors. It's very common for them to break even though you may hear the motors moving.

Max

ptaylor

Thanks again for all the replies!

Recharged the A/C system. The high side meter needle is fluttering or vibrating between 225 and 250. The low side is stationary at 40. Cabin temperature is at 54 degrees with a 115 deg F ambient or 83 degrees F temperature outside with 50 % humidity.


My question is why would my high side be fluttering between 225 and 250?

Rambler65

According to the service manual, spec for 110 degree ambient temperature (as high as the chart goes) is 50-64 degrees outlet temperature. So you're in the ballpark there. However low side pressure is listed as 50-60 psi and high at 300-390 psi, so you may still be a little undercharged. Not sure if that might be contributing to the pressure fluctuation. (Typically that is caused by an expansion valve problem, but the XJ uses a fixed orifice tube.)