The air only blows warm (outside temp) when the car isn't moving. When at a standstill in drive, the engine idles at only about 600 RPMs, but 800 in neutral or park. I'm wondering if this is related...

 

Revs sounds ABOUT right.

The first thought is are the 2 electric fans working??????.

If they are, there are other issues, but I reckon they are not operating with the a/c. There was a rework of the fan wiring to have them ON all the time the engine was running a/c on or off, and that would have them wear out sooner than designed, and maybe 14+ years is that time???.

I rewired mine to be thermo operated, but they are still ON as long as the a/c is ON, and one of these days I will fix that circuit also.

 

This recently happened on my S type. Cold AC air when driving but +at- stops or idle warm air. Turned out it was the AC compressor.

Check the charge with gauges, might just be low on refridgerant. You can pick up a "low side" gauge at Auto Zone and such stores.

https://www.jaguarforums.com/forum/s...ics-faq-55219/

 

Thanks, right now, the fans are blowing fine, so it's not that. It seems strange to be low on refrigerant and still blow cold most of the time.

 

I know it sounds weird but the refrigerant being slightly low could result in not blowing cold at idle but good at speed. Just experienced this in my 1997 XJR so did a recharge and now all good.

When low refrigerant, need to have more airflow through front end than fans can supply.

You can do it yourself with the "low side kit" that Rick was talking about. If you suspect a leak in refrigerant, you can buy refrigerant with a die in it that will show where the leak is.

Good luck.