Jaguar Association of Greater Indiana *
forum user since
Low side pressures on the R134a systems don't differ much from the earlier R12 systems, so usually they run pretty close to 28-30psi. However, the XJS models can be a challenge to try and fill by using pressures, for a couple of reasons. One, they have such a small grill area that they don't flow much air through the condenser sitting still. Two, Jaguar, in their infinite wisdom, had the auxiliary electric fan only run based on radiator temperature, so it mostly doesn't run unless the coolant temp is elevated. Consequently, at idle refrigerant pressures are usually higher then one would expect when at idle. On top of that, checking pressures requires the bonnet to be up so all the air going in to the A/C system is heated air right off the hot engine instead of ambient air. That also makes the A/C performance seem weak.
So the best way to properly fill the XJS system is evacuate, vacuum and fill with the proper charge weight.
I have had a few owners complain about poor cooling in traffic, and have modified their electric fan to operate anytime the compressor runs to counter that. That's not always easy as the fan control circuits pretty much changed every year.
Hmmm! Didn't expect all of that did you?? The XJS is a different breed.
'97 XK8 Conv.