I have a 1995 XJS 4.0 coupe and have a couple of questions about the AC. My AC gets cold, but the R134a leaks out over a period of a few months. Next time I refill the R134a, I'll use some UV dye to try to find the leak.

1. What are the most common culprits for a slow leak? The high- or low-pressure valves? The fittings?
2. How much air should I be expecting? If I have the fan set to 2, for instance, I can hear a fan blowing pretty hard, but not much air is actually coming out of the vents.

Thank you!

 

I don’t think there’s any common point of failure. They shouldn’t fail. There’s absolutely nothing anyone can tell you that will be of any help until you add that dye and see where it’s coming out.

To get ahead of things, you should already get your hands on a drier. If you’re going to open that system up, regardless on what’s leaking, that will need to get replaced.

As far as the lack of air, that’s also not right.
1. Is there air blowing to the feet?
2. What about defrost?
3. How about the air supply for the back seat? (the one at the back of your armrest?)

I have to ask, are the vents open? There’s a side wheel that closes off the air to the diffusers closest to the doors. Those are open, right?

 

Thanks, Vee. I'll definitely get a drier before I do anything inside the AC.

Defrost and the air supply for the back seat definitely get at least some air. I'll have to check about the feet and I will do the idiot check of the vent wheel.

I remember a few years ago someone describing the mechanism that diverts air to the cabin from either the AC or the heater, but can't remember what it was called or how to check it.

 

Do the late facelifts have rear vents as well? In my '92, the only thing behind the armrest is an ashtray (which I think is hilarious - anyone small enough to sit back there is far too young to smoke), and while there does appear to be piping leading down, the footwell ducts incorporate flanges that block air there and direct it out into the footwells.

As to a lack of air, one culprit I've heard about is one of the blower motors not working. They both feed the same plenum, so if only one's working, you only get half the amount of air. Air from the side vents (by the doors) is never very strong, but what can happen (what happened with mine) is that the vent became detached from the piping. In my case I removed the glovebox liner (easy) and could just slip it back on, very easy. Not sure it would be so easy on the driver's side, mind.

 

On my car the fill ports themselves were leaking. They are standard GM parts, so easy to find.

 

Yes, the facelifts do have rear vents. I capped mine off a long time ago, diverting all the air to the front, where the only people who ever use the car, sit.

 

Something to be aware of when checking for freon leaks on your 1995 XJS is the evaporator. I have seen over the years that this is something that can leak and is often overlooked because it is buried in the dash. Part is fairly inexpensive but my understanding is the dash on the '95 pretty much has to come out to get to the part. Good luck with your search

 

Usual suspect is the condenser ( a/c Rad) , if its all oily and full of debris in a corner or along the top, then that's a sure sign its leaking from there, the face lift versions are in very short supply and 4 liter ones are slightly shorter in depth to the 6.0 version, but the 4.0 will work in a 6.0 but its essential that the electric auxiliary fan works as well to help with cooling on hot days in traffic, also always replace the drier bottle, as a matter of course, failure will lead to the compressor oil not getting through the filter and then the compressor failing.
The 3.6 / 5.3 condenser and driers are way different to the 4.0 & 6.0 so make sure you buy the correct parts, don't be fobbed off and don't waste your money buying second and off eBay as they have been removed for a reason in the first place.

I have stock if you need anything, but first get it diagnosed professionally as you don't want to be buying expensive parts for no reason.
with a/c there is no same fault every time, there is a science behind it believe it or not, systems don't need topping up, its a sealed system not a screen washer bottle so the more you use it the more it needs topping up is B.S. don't use a franchise chain , ask locally and find a garage that actually dose not slap the hoses on from there a/c machine , press start and walk away to do a service on something else, gas is rising a a ridiculous rate in expense due to EU rules on there favored new gas, so the days of a £40 re-gas are gone so you need it done properly .. just advice and i am not touting before anyone kicks off...

Pat