AC Problem

tj2kj · **Posted:** Fri Apr 14, 2006 12:32 am

My wife's Grand Cherokee is having an issue with the AC - the compressor kicks on for only about 1 second, then kicks off for about 1 minute, repeating this. Never stays on long enough to get cooling going. I put a guage on the line and it shows 25psi when compressor kicks on - 45psi with compressor off. Any clues to the problem? Thanks...

adamkrz · **Posted:** Fri Apr 14, 2006 6:53 am

Yes,It's low on refrigerant (freon),There's a low pressure switch that's kicking the compressor off due to the lack of freon,You could just go to your local parts store and buy a can of freon with the charging hose and guage and add it yourself-on the guage there's an indicator to show how much psi is the norm when fully charged,Also look for any traces of oil because when refrigerant leaks sometimes leaves oil where it leaks..

tj2kj · **Posted:** Fri Apr 14, 2006 9:00 am

Yeh, that is what I was thinking, but when I attempted to add the refrigerant it was giving me readings that it was full (25psi). When the compressor was off, the reading was so high no refrigerant would enter the system. Could that be because I was on the high pressure side? I only could find one place to connect to and it was on the line between the dashboard and the condenser in front of the radiator.

Jeepjeepster · **Posted:** Fri Apr 14, 2006 9:59 am

Dont know what year it is, but on our grand the Low pressure side is on the left next to the fender, really easy to see. The compressor must be running to put freon in it, if not the Low and High pressure sides will equalize and cause High pressure on the low pressure side. I believe the High pressure hook-up is on the back of the compressor, kinda hard to get them mixed up. [/u]

KJKev · **Posted:** Fri Apr 14, 2006 11:56 am

Well, it's been a while for me, but heres what I recall.

Some systems have a filter screen. Usually located near a major connection.
See if you have such a screen, it may be plugged up.

Of course, the system will need to be evacuated before you open it up.

This will mean taking it somewhere where they have a station to perform an evac/recharge.

Opening the system and letting out the freon to the atmosphere is a major no-no ....you know, ozone depletion and all that.

KJKev

Edwin · **Posted:** Fri Apr 14, 2006 6:46 pm

tj2kj wrote:

My wife's Grand Cherokee is having an issue with the AC - the compressor kicks on for only about 1 second, then kicks off for about 1 minute, repeating this. Never stays on long enough to get cooling going. I put a guage on the line and it shows 25psi when compressor kicks on - 45psi with compressor off. Any clues to the problem? Thanks...

If it is kickin out at 45 psig and kickin in at 25 psig, then you are surely on the "high" side. Look for the larger of the 2 lines, that will be the suction side of the system. It does sound low though. 45 psig is a very low saturation pressure for the "high" side.

Oh by the way, Freon is actually the brand name for DuPont's R-12. All refrigerants are not Freon. What kind of refrigerant does the system use? R-12 or R-134a?

tj2kj · **Posted:** Sun Apr 16, 2006 12:57 pm

It is a 98 GC with 4.0 liter using R-34a refrigerant.
The only 2 connections into the AC system are the ones as described previously. I have been hooking up to the one on the line that runs along the fender (going from condenser to the unit under the dash). This is opposite of what the can of refrigerant said, but according to info on AC systems on the web, this should be the low pressure side. Is there any way to get the compressor to lock on long enough for me to get some refrigerant into it? The compressor kicks on and off so quick that
1. I don't have time to get any refrigerant into the system and
2.. I am not sure on the low pressure reading as the needle is swinging to fast.
Thanks!

Jeepjeepster · **Posted:** Sun Apr 16, 2006 1:25 pm

tj2kj wrote:

It is a 98 GC with 4.0 liter using R-34a refrigerant.
The only 2 connections into the AC system are the ones as described previously. I have been hooking up to the one on the line that runs along the fender (going from condenser to the unit under the dash). This is opposite of what the can of refrigerant said, but according to info on AC systems on the web, this should be the low pressure side. Is there any way to get the compressor to lock on long enough for me to get some refrigerant into it? The compressor kicks on and off so quick that
1. I don't have time to get any refrigerant into the system and
2.. I am not sure on the low pressure reading as the needle is swinging to fast.
Thanks!

There is a way to short out the wire that connects to the compressor but Ive never looked into what wires. Mine always kicks on AFTER i hook the can up, even if it never kicked on before I hooked the can up.

adamkrz · **Posted:** Sun Apr 16, 2006 8:49 pm

It's R-134a refrigerant and I'm not sure but I believe you can't tap the high psi side with the charging hose givin,When you start charging the system the compressor will start running longer as more refigerant enters the system,Put the a/c in the high speed mode-It will help if it's done on a warm day with the sytem under a load,You could also look close to see if there's a S for suction and D for discharge on the compressor somewhere..

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