Air con AC ready for the heatwave

Hello all,

The AC on my 2004 XJ8 seems to be working normal when cold but in traffic when it gets hot the AC will not work but when traffic is free it will slowly work again. Also when I give it the beans it will also cut out and come back on when I cruise.
The garages here have recharged, washed the radiator and refuse to do more. I have plugged in OBD and no faults. Would a kind person shed some light please?

Kind regards

I changed my mind. Can’t say expansion valve conclusively.

Thanks for the super fast reply John. I will follow your suggestions to check those valves and report back! Oh bugger it I will just replace them both

Is the fan in the dash ducting working? If not, air will only pass through the aircon heat exchanger coils when the car is moving.

Hi Graham,

Yes it is working. It only loses AC cold when car is idling hot in traffic or when I give it the beans. Cooling fans working too

At full throttle the AC compressor is disengaged.
I have no idea what the problem might be at idle.

A/C compressors are not very efficient at low RPM especially when they become older and worn.

You might try to put the gearbox in NEUTRAL and increase the engine RPM to see if it starts cooling again while in traffic.

I tried your method by increasing RPM, seemed to work but back to warm air after 30 seconds, not good in todays 36c and 95% humidity🥵

Check the fans (under the bonnet) are running at a slow speed when the air con is on

Oh well, the serpentine belt snapped because the AC compressor seized. Will see if that was the problem or part 2😅

The culprit would most likely be the AC compressor was in the way out. It seized, snapped the belt so replaced it, the AC radiator and all is well now…Now for the erratic revs…

I don’t know if this has anything to do with your issue, but IIRC our X-300s (and probably the X-308s as well) have a tiny intake fan “sensor” that is located somewhere behind the dash on the passenger side. It’s function is to “sample” the cabin air from time to time whenever the (A.C.?) is on … I guess to determine it’s temp and possibly humidity level (?) and adjust the fan speed and/or cooling level accordingly. IIRC, in connection with that unit, there is some kind of set up that determines whenever the car is stopped, e.g. at a traffic light, traffic, etc., and makes similar changes to the HVAC system accordingly. I think what it does is that it causes the cooling level or fan speed to be increased slightly while the car is stopped, b/c of the fact that (some) air is not flowing through the HVAC system naturally due to movement of the car. In fact, if you listen closely with all other noise sources off, you can hear the fan speed increase upon stopping, and then slightly slow back down when the car starts moving again. When the unit is going bad, that noise can actually get quite noticeable, driving the owner/driver crazy until they figure out what’s up. :crazy_face: Motorupman, is that an accurate assessment? :confused: