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Discussion Starter · #1 ·
Hello again. I have another question that may or may not be related to my previous question in regards to my jeep running a little hot.
The vehicle is a 1998 jeep cherokee 4.0L 4 speed automatic w/overdrive 4WD with 156K miles. This particular problem has to do with my AC. With my AC on max, the system is not pumping out cold air. Its not hot air, just not cold. I purchased one on those $22.00 white cans of 134A refrigerant that comes with the little gage from Walmart. I can't get a good reading on it because of the following.When I hook the gage up-that comes with the 134A can-to the low side(bigger hose) valve stem, and the compressor is off, the little needle in the gage goes up to 63psi. When the compressor comes on-for about 5 seconds-the needle goes back down to 15psi. It continues through this cycle while the AC is on Max. When I go to low cool, it does the same thing except the needle goes up to 65psi when the compressor is off and down to 15psi when the compressor comes on.
Does anyone have any idea of what I can check or what if anything is bad.
As always, all recommendations/responses are very much appreciated.
Thanks,
Robert D.
 

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Low gas will cause the compressor to cycle on and off. It is a safety thing to keep from destroying the compressor. If you add some gas it will come on and stay on. There is a lot of high pressure in an ac system so pay close attention to what you are doing. You will have the best luck getting gas into the system if you invert the can.
 

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newdad1 said:
down to 15psi when the compressor comes on.
Should be 35-40 psi, w/compressor clutch engaged and turning the compressor.

It will cycle quickly (or not at all) if the refrigerant is low.

Add some refrigerant and see if things improve AFA how quickly the compressor cycles and the air temp.
 

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Hates: Liver. Loves: Diesel
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Really tough to diagnose with one gauge. I think A/C manifold sets are only like $40 at Harbor Freight, and they'll really let you diagnose better. Just using one gauge to recharge can very easily cause problems. If you have a restriction in the condenser or the expansion valve, and you're charging one side, the other side could be spiking wildly.
 

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Discussion Starter · #5 ·
I inverted the can and was able to get some of the gas(freon) into the system. For the record, the place that I hooked up to was the valve stem located on the larger pipe/hose between the compressor and a piece of equipment that looks like a small aluminum colored canister about 10" tall and 4.5" diameter close the the firewall on the passenger side. I am not sure if that is the dryer or not. In any event the compressor is no longer cycling. It is a steady 37 psi. The air seems a little cooler also. This was all done with the system on max ac. I still think it will get cooler, but still not sure how to get it there. Maybe I should just leave well enough alone. I still have to clean out the bugs and road grit in front of the evaporator(its in front of the radiator, but connected to the compressor.

Anyway, thanks for helping me out, and saving me $$$$.

Rob
 

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My 2 cents worth
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cobalt327, I disagree, the low side should be between 28, and 30 psi, just so as long as the compressor cycles on and off slowly, with the throttle speed raised.

curtis73, you are right on, with your recommendation, of the proper gauges.

The high side pressure should not go above 225 PSI, the low side pressure should hover around 29 PSI, if it cut's out on the high, or low side, a pressure switch, could be faulty. I say this 'could be' only because I have found, a bad fan clutch, or worn out electric fan motor, or non-working fan relay, or switch have been at fault, many times before. I check this by spritzing water across the condenser. It may also have the wrong 'fixed orifice' for the current freon.

The 'fixed orifice' is installed in the high pressure line, generally in the line that goes into the the evaporator case. The system has to be evacuated fully, and the fixed orifice needs to be inspected for any debree. Any debree on it, has come from your compressor, and this is time for a complete system flush, and a major parts replacement.

PAG 100 oil replacement, is common, and using a 'blue', or 'brown' fixed orifice, is common around here, when changing to R134A.
 
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