hey Guys, my a/c compressor cycles on and off continuously, even when I select manual temp control set to max heat. is this normal ? ambient was about 15c when I checked. Where to start to fix if this is an issue?
BTW Fan speed set to Normal

 

At 15c the a/c would be getting so confused, especially the old style systems in the XJ-S.

Being a Conv, the a/c is wired to run ALL the time, unless a by-pass is installed, and we have ALL done that pretty much.

I reckon the cycling would be considered "normal" in my opinion.

 

Grant is correct. I'll just add a bit more.

The climate control is designed to refrigerate all incoming first and then heat it as needed. This is to dehumidify the air for comfort. Thus, the compressor is engaged no matter what temp setting the driver asks for....even max heat. The only way to turn off the compressor was to turn the climate control 'off'.

However, turning the system 'off' meant that the fuel wasn't being cooled, as the fuel cooler depends on the compressor being engaged. Jaguar originally didn't worry very much as they felt that it was unlikely that owners would drive around with the system turned off....especially coupe owners, and especially not in warm weather when the climate control was most likely to be desirable.

Somehow, though, the notion hit them that *convertible* owners would very likely be enjoying top-down driving in warm weather. And, more often than not, driving with the climate control 'off'. No fuel cooling.

So......

Circa 1989-90 Jaguar changed the circuit on convertibles so the compressor stays engaged all the time....even with the controls set to 'off'...so the fuel was always being cooled.

Cheers
DD

 

Thanks for the info guys, looks like one less thing to fix

 

I am not getting any cool air...seems the heat is on all the time regardless of the temp setting and/or the fan setting.
HELP it is hot in Florida

 

You do not say which model or which year you have, but if you have on your car the Delanaire III aircon unit you should have the manual over-ride option. If you can pull out the LH knob it should click and tuned to full cold freeze you in no time. If this works and cold air comes, then the problem is a little electronic part in the automatic control system (name I do not know) and when this little part fails, the system no longer registers the temperature of the air (or something like that) and makes the control system think it is totally cold outside so the system defaults to full heat unless the manual over-ride is activated. If pulling out the knob makes no difference (or it does not click out, meaning you have the Delanaire II unit, models pre-about 1988/89) then the aircon is not working for some other reason.

The part is replaceable, is still available I think (certainly was a few years ago), and is surprisingly expensive.
Greg