Automotive Air Conditioning Information Forum (Archives)

CrypticOne on Thu July 31, 2014 11:31 AM

Year: 2004
Make: Jeep
Model: Grand Cherokee
Engine Size: 4L
Refrigerant Type: 134
Ambient Temp: 83
Pressure Low: 33
Pressure High: 400
Country of Origin: United States

When I purchased my WJ the AC didn't run well. For the most part I have just used it for a couple years with the windows down in the summer time but this summer has been hotter then most here or I am less tolerate. LOL

Anyhow I took it to a tire change type place offering free AC inspections. They wanted to replace the compressor, ac drier and expansion valve for a cost of over 1800 dollars.

I rented a gauge set for auto zone and followed some the basic instructions I found on the forum for testing the system. Here are the results but I am not too sure how to interpret the data I have collected. Any help would be much appreciated. Best I can figure I have problems on the high side of the system.

DATA
Outside Temp 83 Degrees RH 42%
Static Pressure about 96psi

System Running
Windows Open
Ac Blower Set to Max
System set to recirculate
Crappy box fan set to blow on radiator
Electric Fan running on high

700 RPM Engine Idle Low Reading 30psi High Reading 380psi Temp at Center Vent 53Degrees Passenger Vent 70 Degrees.

1500 RPM Low 30psi High Surges to 475psi and compressor shuts down and restarts. Cycling over and over.

I wanted to add that the blend doors seem functional and the recirculate door does as well. I am not sure why the big difference in temps between the two sides. This is a single zone system. I do feel warm air coming from the floor boards at times even though the flow is set to the main front vents.

HECAT on Thu July 31, 2014 1:26 PM

When you had that free check, did they happen to recover and recharge. Do you know it has the right amount of refrigerant in it by weight?

Try and mist some water over the condenser while running the test and see if the high side pressure drops. If it does you have heat rejections issues (dirt, air flow, fan etc.) with the condenser. If it does not, your system may have other issues. Try the mist test and report back what you find.

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CrypticOne on Sat August 02, 2014 9:20 PM

Okay. So some updated data.

85 degrees 19%RH static pressure 115psi
No water misting
700rpm 28psi 340psi high
1500rpm high surges to 450psi and shuts down

Water hose lightly misting on ac condenser
700rpm 24psi L 240PSI H

Had a real hard time holding 1500rpm
Made a video of the gauges while attempting to hold 1500rpm with the hose lightly misting.

At times the low was drawn really low to like 15psi. The unit still cycled a bunch but pressures were much lower on the high side.
http://youtu.be/ilP84CngIYE


They didn't evacuate the system at all. Not sure how much refrigerant is in there.

Thanks,

Cryptic

HECAT on Mon August 04, 2014 7:10 AM

Not knowing history (it may be overcharged, it does not seem to be leaking). I would recover, vacuum, and recharge to spec. Clean the air flow path of the heat exchanger stack (condenser, radiator, etc.). Make sure all stack side seals and shrouds are in place. Make sure fan(s) coming on and functioning properly if electric. Replace tired fan clutch if mechanical. Make sure there is no re-heating of cabin air from heater system.

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Dougflas on Mon August 04, 2014 9:31 AM

Also make sure the electric fan is blowing in the correct direction.