Problem with A/C

[Ben824]

Ok so there is a good deal on a 2000 XJ for sale not too far from me and I was thinking of making a purchase except the seller says there is a problem with the A/C.

He describes the problem as at idle the pressure in high pressure side realy builds up and the air becomes warm.

Now I am guessing since the pressure builds up that the compressor is fine but beyond that I am not sure what might be wrong. If anyone has any clue to what might be the problem I would love to know so I can figure out if in total that this XJ would be a good buy.

 

[ehall]

sounds like the compressor is not able to fully compress the refrigerant at low RPM, might just be low on refrigerant

 

[Ben824]

I guess I can suggest to him to try one of those inexpensive re-fill kits from autozone and see what happens.

 

[Ivan]

This problem typically arrises for the later model XJ's. It's most likely the low pressure switch on top of the accumulator. It's a simple swap out. Just get a new one at the dealership. You won't lose any refrigerant when you replace it, as there's a schraeder valve there to keep refrigerant in.

What's happening is that your evaporator is icing up and blocking air flow, which is why you are getting the warmish air. Once the ice melts, after you've let you rig sit for a while (about 20 minutes or so), the AC will work fine until it ices up again, and the cycle repeats.

A tale-tell sign is large amounts of water under your rig once its sat for a while. That's all the ice melting off.

Low refrigerant could be another issue as well.

 

[Ben824]

This problem typically arrises for the later model XJ's. It's most likely the low pressure switch on top of the accumulator. It's a simple swap out. Just get a new one at the dealership. You won't lose any refrigerant when you replace it, as there's a schraeder valve there to keep refrigerant in.

What's happening is that your evaporator is icing up and blocking air flow, which is why you are getting the warmish air. Once the ice melts, after you've let you rig sit for a while (about 20 minutes or so), the AC will work fine until it ices up again, and the cycle repeats.

A tale-tell sign is large amounts of water under your rig once its sat for a while. That's all the ice melting off.

Low refrigerant could be another issue as well.

Where exactly would I find that low pressure switch? I am only somewhat familiar with the different components of the AC system.

 

[Ivan]

Where exactly would I find that low pressure switch? I am only somewhat familiar with the different components of the AC system.

Follow your AC lines from the compressor, back towards the firewall. You'll end up at a longish black tank looking thingy (the accumulator). On top of that is the low pressure switch, with associated connector.

 

[kennzz05]

make sure the electric cooling fan is running as well that would cause that