Hi, I'm working on 2 XJs (99 Classic, 00 Sport) and I'm stumped on the AC problems. Here are a few of my observations:
99 Classic:
Low pressure port reads 70 PSI from an AC recharge can. (75F ambient)
Compressor turns on and off
Center vents aren't blowing (I think it's clogged)

00 Sport:
Low pressure port reads 40 PSI (85F ambient)
Compressor only turns on when low pressure switch is bypassed with paper clip
Low pressure port goes to zero when compressor turns on. Goes back to 40 when paper clip is removed.

On both, this line going from condenser to the firewall gets ice cold: (no other line gets cold)



I'm thinking both are either low on refridgerant, or have too much. Both probably have leaks.
Just looking for some guidance and suggestions. Thanks

00 is low on refrigerant
Do you have air coming out the defroster vents when on. And when it is running does the return line get cold to the touch?

Thanks for the reply. I'm pretty sure defroster vent air is coming on the 00. Not sure about the 99 but I'll check tomorrow. Throughout my tests the line in the picture is the only one that gets cold. Lines connected to the compressor get hot and lines connected to evap canister are same as ambient temperature

If it’s blowing on the defrost position only, my vote is for cracked vacuum lines. The lines should be found on the right front fender, in the engine bay & those lines should run to the round vacuum canister behind the right front bumper. Some times the connection nipples break on the round vacuum canister.

So far, I concur.

On the 99, if the blower is on (no need to run ac to test this) check the defrost vents. If you feel the air moving when the selector is set on floor or dash vents, you have a vacuum leak in the HVAC system like MaskedMallard said.

The '00 is definitely undercharged. Here's the table for high and low pressure. My advice is don't trust the low pressure gauge on the recharge can, get a set of manifold gauges so you can also read the high pressures. Bear in mind these are pressure when the compressor is running. A "rule of thumb" suggests that with the AC off, engine cooled down, low and high pressure side (once equalized) will be about ambient temp. Not a hard fact, but seems to apply.

Is the reading from the 99 when the compressor is running or off?

I don't see anything particularly wrong with those numbers

Sorry to those who responded, I've been pretty busy and haven't been able to get to this. My brother has the 1999, and air comes out on the top right and top left vents and the defroster vents on all settings. On my 2000, I think air comes out of all vents on all settings. The AC stuff is pretty expensive though, I'll probably wait till spring and worry about it then. Thanks again all

It would be better to check pressure using a manifold gauge set so you can see the high side as well. You can pick up a set pretty cheap good enough for home use and there are plenty of videos on youtube showing how to use the gauges. Those "recharge cans" are pretty useless for doing any real diagnosis. You also have to be careful because a lot of them contain sealers that can damage your AC system.