My AC has started to act up. It will run ice cold then over about a 5 min time it will gradually stop cooling so I turn it off and continue driving got 5-10 minutes and then turn back on and it is cold again.


I checked my system pressure and have 26psi with AC running on high, turn AC off and pressure goes up to 46psi, this is within the full marking on my gage.


An ideas what my problem and correction would be?

 

You could have a bad low pressure cycling switch that is keeping the compressor on all the time and freezing the evaporator up into a block of ice.

 

Running it on MAX? That can cause it to freeze up in high humidity conditions. Is it humid at all in North Carolina?

 

Also signs of a bad compressor clutch

 

Generally icing is accompanied by reduced air flow throughout vents.

The later XJ's do not have any evaporator temperature sensors, compressor cycling is all done through the high and low pressure switches.

I would check to make sure your compressor is turning. What happens is the clutch plate wears and needs to be reshimmed, otherwise it will work intermittently after its been on for a bit.

 

Your low pressure might be going lower than what you think when you are actually driving and have some RPMs up. According to my factory service manual, the low pressure cycling switch contacts open up when pressure drops below 20.5 PSI, and close again once it's back up to 34-38 PSI. Do you notice frequent cycling when it's on high?

Your low side pressure while running at idle with the system on high should be around 32-47 pounds depending on ambient temperatures between 80 and 90 degrees, and you don't get that till you shut down the motor, which allows the hi and low sides to equalize. 26 sounds like low freon. High side compressor discharge pressure should be between 250 and 300 PSI at around 90 degrees ambient.

As others have said, icing may be your issue as well, but living in Texas, we wrote the book on humidity, and I've never had mine ice up, even when it got low on freon.

 

Worn AC clutch. Wire brush the clutch faces and remove a shim.

 

I did this a year or so ago and it fixed the problem, though it's only a matter of time before it fails completely.

 

I did mine 6 years ago based on a John Deere combine video and it's still working. Shimming the clutch is not exactly "getting it through the summer".