Hi guys and girls, we are at last having some good weather here in England and have needed to use the a/c,
I had the system vac'd and gassed after i replaced the engine in the old girl last year. Now the a/c works fine for about 15mins then starts to go warm, if i turn it off and roll down the windows and leave it off for a period of time then turn it on again it is fine again for about 15 mins then goes warm again, any thoughts as to what this might be.
thank you, Gary.

 

low on freon?

 

I'd say low on gas and cutting out on a pressure switch. I had my XJ topped up twice, then gave up and removed it all. These systems need to be run often to keep seals up to scratch, so I've been told.

Rob

 

man scotland, england looks like the forum gettin big haha all we need is for a welsh guy to pop up and we got my complete heritage!

 

It is possible it is a vacuum leak allowing the heater core to warm up?? Maybe.

 

i had the same trouble and found the low pressure switch to be at fault in my zj ZJ's rule

 

re-gas it and search for leaks?

 

What's the function of the pressure switch in the A/C system?...

 

The purpose of the pressure switch is to cut the system off so that it will not cause damage if pressures are not in spec. Now on a 1997-2001 Cherokee, the pressure switch does have more function that I have determined. One of its functions is controling the cycling of the compressor clutch. On my Jeep, I have found that because I had a bummed out low pressure switch, the compressor clutch was never disengaging when the system was on, hence causing evaporator core freeze up. Another fuction of the switch is to monitor the temperature of the refridgerant that is cycling in the system. If the compressor stays engaged and does not disengage, the refridgerant will keep getting colder hence, lowering the pressure and causing ice to form. Does the low pressure line on your Jeep produce a thin layer of ice when the system is running? If so, I would try changing the pressure switch, they are like $20 US the parts store.

 

May have a restriction someplace in the system that is causing it to freeze up and plug the line. Look for a heavy frost line on the hoses and hard lines, that will be the spot that is restricted.

 

ahhhhh... thanks !

 

x2.. check this
The fixed orifice tube is installed in the liquid line (left-hand drive) or liquid line jumper (right-hand drive) between the outlet of the condenser and the inlet of the evaporator. The fixed orifice tube is located in the end of the liquid line or liquid line jumper that is closest to the condenser outlet tube.
The inlet end of the fixed orifice tube has a nylon mesh filter screen, which filters the refrigerant and helps to reduce the potential for blockage of the metering orifice by refrigerant system contaminants Fixed Orifice Tube - Typical The outlet end of the tube has a nylon mesh diffuser screen. The O-rings on the plastic body of the fixed orifice tube seal the tube to the inside of the liquid line and prevent the refrigerant from bypassing the fixed metering orifice
OPERATION

The fixed orifice tube is used to meter the flow of liquid refrigerant into the evaporator coil. The high-pressure liquid refrigerant from the condenser expands into a low-pressure liquid as it passes through the metering orifice and diffuser screen of the fixed orifice tube.
The fixed orifice tube cannot be repaired and, if faulty or plugged, the liquid line and fixed orifice tube unit or liquid line jumper and fixed orifice tube unit must be replaced.
Like the op suggested check for frost on the lines , this may indicate a blockage.
Good luck!

 

How do you remove the liquid line/ orifice tube. I can't seem to pop mine off.