I've got a strange air conditioning problem with my 2004 X350 XJ8.

The aircon is nice and frosty for about the first 20 minutes of driving but after the car is warmed up it no longer works.
I've had the scanner on it and most sensors seem to be what you expect, except that when the aircon stops working I see the radiator variable fan duty cycle go down to 10% or less. Otherwise in the initial 20 minutes and with the aircon on, the duty cycle is 50% or more. In fact if I turn the a/c off and on again, the the fan speeds up again to 50% plus and I get a burst of cold air. However, the fan goes back to 10% after only a minute or less.

I'm thinking the airflow through the condenser is the problem.

Am I right in thinking the radiator fan in front of the condenser should be operating at 50% plus whenever the a/c is on?
I put the climate control to the lowest setting "LO" to make sure the a/c is on but still the fan stays down at 10%.

The fact the fan can in fact go up in speed, either initially before the car has warmed up or just briefly if I manually turn a/c off and on makes me think the fan itself is not faulty?

Also I was wondering whether the a/c pressure sensor controlled the radiator fan in some way, however, it seems to operate between 1.6V and 3.2V, which I think sounds right?

Bit of background. The a/c failed and I took it to a auto electricians to fix.
Initially he found the pipe between the compressor and the evaporator had failed. (Ordered a new one and replaced.)
Then he found that the compressor had failed, probably because it was running while dry. (Ordered a new one and replaced.)
The a/c would only work for a while and then stop.
Then he suspected the condenser was blocked and didn't improve after flushing. (Ordered a new one and replaced.)
Then he noticed a DTC for a solenoid fault detected. (Replaced the compressor solenoid, even though it was a new compressor.)
Problem still persisted. Decided that the "new compressor" was faulty. (Replaced compressor again with a new Denso compressor.)
Slightly better but still the problem exits.

Thus I got out the scanner and have noticed the radiator fan slowed down after a while and this coincides with the a/c cooling stopping.

Any ideas would be appreciated?

 

I finally sorted it out and thought I would update the thread in case anyone has a similar issue.
It came down to fault in the RCCM (Remote Climate Control Module).



I got another RCCM unit and installed it - 2W93-18D493-BE. This made a difference in that the A/C seems to now seemed to at least work, however it was continuously at a fixed temperature. (I think it is a 25 degree fail safe value?) You couldn't control the temperature or fan speed etc. etc. It would seem that the unit has to be programmed for the individual car or maybe just model? The same unit is used on a lot of different jags.



So I opened the case on my original unit and found some burnt out resistors on the bottom of the board. Checking the other unit, they seemed to be four 2 ohm resistors in parallel, probably 1/2 watt or 1 watt. So I replaced the four burnt resistors with one 5W 0.5 ohm resistor and put a couple of leads on it so I could put the resistor on the top board.

All the A/C functions worked and nice and frosty. All fixed.