Hi, everyone, I have a strange problem to relate - yesterday my air conditioning in my 2002 XKR convertible was working, although I felt it might be time for a top-up to get the temperature down to where I would like it - I bought a can of A/C Pro (formerly STP) from Halfords and connected the trigger to my car, (before connecting the gas canister), where the gauge went right up to the top of the scale and wouldn't budge, whether the engine was running or not - it is supposed to indicate the level of refrigerant pressure of course - Anyway, I thought that must be some kind of anomaly because the aircon was performing OK, so I connected the gas canister but the reading just didn't budge off the top of the scale, although it didn't feel as if anything was going in, and it certainly wasn't making my a/c any cooler, which by now was getting warmer because of the small escape of gas every time I disconnected the system to retry it! - anyway, I used the canister on my other car to see if there was a problem with that one and it seems to be ok - so I tried again, this time weighing the canister before and after trying to fill the system and it seems to be going down by about 20grams each time, which is probably what goes in the trigger pipe each time it is reconnected!
So can anyone suggest what on earth is going on? If there really was that much pressure in the system surely something would blow, and it certainly wouldn't be working properly, which to all intents and purposes it was until I stupidly messed with it! any ideas welcome - thanks

 

That sounds odd. If the gauge on the low pressure side is showing in the red zone with the engine running at 2000 or 3000 revs then I definitely would not be connecting the cylinder and trying to add more refrigerant as you've clearly not got the information you need to know whether the pressure is in the green zone or not.

You must be using the 13mm low-side port as the connector on the gauge will not connect to the 16mm high-side port.

I've found the gauge works fine on both our XK8 and XK so something is not right.

You are using the R134A cylinder and not the "universal" stuff that Halfords sell .... although I don't think that would cause the issue.

The only car I've had which didn't behave properly with exactly the same equipment was a 2010 Ford Mondeo which I obviously over-pressurised even though the gauge was showing in the green zone. Once I got the pressure back down it was fine but the upper reaches of the green zone were too high for the Ford.

I think that I would take it to one of the a/c quick-fill tyre places and see what happens when they try.

Richard