The heater on my 01 XJ8 VDP seems to be working correctly, except for one instance recently:
We had a really cold spell, with temps down below 20F (about -7C). I started the car, and let it warm up for maybe 15 - 20 mins before setting out for a drive. By then the temp indicator was right in the middle of its normal range. The heater would not put out anything but cold air. This was with the AC switch "off" (of course) and the air flow selector set to both dash and floor vents. Pushing the recirculate button made the exiting air a bit less cold, but not even lukewarm. Eventually I tried switching the air flow selector to dash vents, and the air promptly heated up. Ditto for going to the floor vents. But going back to the joint dash/floor setting returned the cold air.
Does anyone have an idea what was going on? I have a Ford with automatic climate control, and in that car the joint dash/floor setting turns on the AC compressor. Does the Jaguar system work the same way? Didn't see anything to that effect in the owner's manual. But in any event, I thought the AC compressor was always disabled in very cold weather (Jag or Ford).
We have warmed up to the mid-20s and 30s now, and heater operation seems to have returned to nominal. But I am puzzled.