ptaylor

Greetings Jeepers!

A/C blows hot, help!

So...after fighting the non-working A/C in my jeep for almost a year it still won't f.... work! Here's a breakdown
1) Replaced all a/c mechanical parts (compressor, condenser, evaporator, a/c drier, a/c liquid lines, rubber o-rings, hoses) with Rock Auto parts. NAPA compressor, OCF condenser, Spectra Evap.
2) Evacuated and filled a/c with refrigerant professionally, checked for leaks with dye in system (1.25lbs + 0.5lbs after it wasn't working per tech)
3) Gauge Readings (80 deg F): 300 high/40 low, but 350 high/40 low when compressor kicks on.

Any help or advice would be greatly appreciated! Thanks!
4)

Rambler65

I assume that once it kicks on the compressor keeps running. If not then there's an electrical or sensor problem somewhere. If the compressor cycles on and off rapidly you won't get much cooling.

That high pressure sounds a bit too high for 80 degree ambient temperature, more typically you'd be seeing around 200-250 psi. Here's the temperature/pressure chart from the 1999 XJ shop manual:


(I think there were changes made in the XJ's air conditioning system for 2000 but pressures should be the same.)

If the AC is basically working the high-pressure line should be hot and the low pressure line should be cold. The following video shows how to use an infrared thermometer to check that your condenser is doing its job. You can similarly check for restrictions in the refrigerant lines:


Sanden (compressor manufacturer) provides a pretty thorough diagnosis chart:

https://www.sanden.com/objects/SANDE...OSIS_CHART.pdf

Have you checked your temperature blend door? Perhaps the evaporator is getting cold but you're only getting air from the heater core.

motowood

I've come across a few xj's with an A/C compressor that cycles on and off quickly but does not cool the air and I have fixed them all. This is good actually, if the compressor is cycling it means your compressor is protecting itself from overheating by shutting off, then on, then off etc. If it does not come on - you have a bad compressor.

Assuming your compressor is cycling there is a trick with these xj compressors. You must remove the compressor from the engine bay. Take it to a work bench, underneath the pulley that connects to the belt there is a small washer. Remove this washer. Put it all back together and reinstall on your Jeep. Viola, AC fixed! Search youtube I believe there is a tutorial...

Stay cool!

ptaylor

Thanks so much for the replies, gents!

The high side is hot to the touch (i.e. compressor rubber hoses) and the low side (i.e. liquid line to evap) is cold as all get out! Ran water on the compressor, no luck! The tech put a bit more refrigerant in..bupkis!!!

I think there is something to be said about using aftermarket parts. I wonder if the volume decreases with using these parts or if they function differently? I've read that some evaporators for example don't have the same construction inside so they don't work the same? With a huge 4.0 blowing air across this tight fitting engine bay and into my compartment, I wonder how "finicky" these systems are? The tech who recharged my system told me there is a growing consensus among professional mechanics that only an OEM evaporator will work inside these 4.0's? He mentioned that even he had a customer who had all his a/c components changed several times and the only thing that got the system to work properly was an OEM Mopar evaporator? Who knows man!?

In regards to the blend door, it mechanically worked fine when I took out the HVAC box. So, I assumed it was good to put back together. I'll have to research how to check the blend temperature door. I am a novice obviously, so I think the blend door is a simple mechanical apparatus (door) that cuts off or separates air flow from the heater core?

Oh well! Can't say thank you enough! I'll give her another go here soon. Happy wrenching!

Rambler65

I would say from the description of your hose temperatures you're getting at least some cooling. Your AC guy should have charged in the proper amount of refrigerant by weight and pressures indicate the compressor is pumping, so you should have decent refrigerant flow. I don't think there's anything particularly exotic about the XJ evaporator. If the old one is about the same size with similar tubing and fin area it should work substantially the same as the OEM part. Search the board here, a number of people have replaced evaporators with aftermarket parts and the main issue with some of them seems to be fitment rather than functionality.

I'd definitely check the blend door. In the XJ (at least later ones) the heater core is always hot with the engine running. The blend door determines how much air comes into the passenger compartment from the heater core vs. ambient or refrigerated air. Your AC system could be otherwise working perfectly but if the blend door is only letting through air from the heater core you'll just get hot air. If you search the board you'll find a description of how the blend door can be operated manually from under the glovebox area.