My soon to be friend (cute girl) has a '94 XJS 4.0. She doesn't drive this car much (prefers her H2 for some reason). Her AC stopped working. She's taken it to a few different places and got quotes of anywhere from $350 to $500 to replace her defective AC pressure switch. I see the switch is only about $70.

Can someone tell me if that switch is on a Schrader (sp?) valve, or does the system need to be evacuated to replace it. Is this easy access to this switch? Is that system R12 or R34 (originally)? I haven't had a chance to play with it (or her) yet, but I've repaired other systems (O-rings), and refilled systems on quite a few different cars.

Just want a heads up before I tell I'll get dirty for her.

 

During the '94 my is when Jag switched from R12 to R134. You will have to look at the service ports to determine which it is, could be either. My '94 6L coupe is R12. I believe the pressure switch is on the compressor, but I don't have any advice as to if wt can be done without evacuating the system. I kinda think you will...

Dave

 

Thanks Dave. I've been looking at diagrams of the AC lines and thought I saw the switch being on the high pressure line below the evaporator, but might not have been specific to the XJS. I'm thinking that if the did the switch from R12 to R34 in '94, there's a good chance it has a schrader valve if it's R34, and doesn't have it if it's R12.

Looking at the big picture of the switch on Rock Auto parts, it appears to have external threads, which would also indicate no Schrader valve.

More Information for FOUR SEASONS 20890

 

Ummm, no, you need to check your terminology...a schrader valve (like on a tire) is the R12 type. The big diameter locking type connection with the ball valve is for R134 (not R34).
Either way the high pressure switch is a part of the compressor.

Dave

 

Thanks Dave. Without having the car here to look at, I'm having to rely on folks with experience, like you, that can say "Been there, done that". Yeah, I shouldn't post when I've just successfully finished something on my car. I expect others to read what I'm thinking, not writing.

The diagrams that I've been looking at are for the 4 level pressure switch. Just noticed it's for an XK8. So accepting it is part of the compressor (which would explain external threads on the switch), do you think that is in an accessible area? Can it be replaced without evacuating the system?

Bob

 

No valve. All the refrigerant will spew out. Did it on my 95 thinking there was one there. And ended up with a rain of r134 all over myself, my engine and the garage roof.

These don't usually go bad. See if the connector or the wires are the problem. When I replaced mine I still had the same problem as with the old switch (shutting the compressor down), and it turned out to be the connector.

Good luck