Hi all and happy motoring for 2013!

I can't work out if the switch pulled out is on or off on the aircon? It all works fine and was great in the summer but now it's colder weather I can't remember, you dont see the engine revs drop on the v12 I suppose as a percentage of power it does not really matter?

Dumb question I know

Nick

 

Try it with the bonnet up and you should be able to hear the compressor clutch relay clicking in or out when you pull/push the switch, assuming that it works of course.
Low gas pressure will stop the relay from engaging.
I think that it should be pull for activate but mine doesn't work so I've no idea!
Happy 2013

 

The compressor always kicks in with heat or cold in the XJS no matter which system IIRC, the push/pull refers to "Auto" mode of operation on the Delanair MKIII system. You don't list which year XJS you have so there's no way to know to which you refer...Delanair 2 or 3. If you put your vehicle in your sig/tag it will make it easier to answer any questions since the XJS between years has so many differences.

 

I was told that unless you have the newer facelift AC, the only way to turn it off is to turn the control on the right to the off position at the bottom.
I never understood why they don't have a fresh air control if you don't want the AC. It's either AC or nothing. Even the heat uses the compressor. GREAT for mpg!! UGH
On my 88, pulled out sets the temp and shifts to manual, pushed in sets automatic climate system, which i must say works rather well on my car.
The BEST thing I did to the climate control was to track down the double vent for the center fascia. That center fixed vent pushed all the air to the back of the car. They're scarce as hen's teeth but they do pop up on ebay on occasion.

 

I've seen it a few times; what is IIRC?

 

If / I / Remember / Correctly

 

Use the XJ40 center vent...way cheaper then the late XJS double vent...I put one in my 86 by trimming the outer rollers...fit like a glove $40 on ebay vice $100+ for the late XJS dbl. The Comp kicks on all the time because it is "air-conditioning" not just cooling. The evaporator also dehumidifies the air when using heat/defog/defrost. Some run an on/off switch through the compressor pwr line to be able to turn it off when using heat.

 

Good idea for comp switch. Any chance it could stir up any electrical issues? I never know with the wiring on this car!

 

Here's a tidbit:

A car with the "pull-for-manual-control" control feature has the MkIII system. The MkII simply didn't have that feature at all.


Cheers
DD

 

Nope. It's a fairly common modification. The glass might have more tendency to fog as the air won't be dehumidified but, if that happens, simply flip the switch to engage the compressor again.

Cheers
DD

 

Another tidbit:

Somewhere along the line.....maybe 1990-ish....Jaguar reconfigured the compressor circuit on *convertibles* so that the compressor stays engaged even with the mode switch turned to "OFF" position. This was done to preserve the fuel cooling function of the system.

The rationale was that, in warm weather, when fuel cooling would be most needed, the owner of an open car would likely have to top/hood down and the climate control system turned "off".....and fuel cooling wouldn't take place.

The real world necessity and effectiveness of the fuel cooling has long been debated. I might add.

Cheers
DD

 

Does that apply to the Cabbies too, even though they are earlier?
I was debating on removing the a/c compressor completely as the system doesn't work at the moment (allegedly de-gassed to change spark plugs) and I don't know if I can be bothered to go to the trouble and expense of re-gassing it only to find out that there is something else wrong.

 

I don't think so. I think the cabbies were out of production by the time the change was made.

Looking at the S57 Wiring Guides the first indication of the change is in the S57/89 edition where it is absent in the S57/88 edition.....where "89" and "88" refer to 1989 and 1988 model year. Although model year designations get very fuzzy I still think the cabriolets would not be included.

On (very) cursory examination it appears that the convertibles had a slightly different wiring scheme at the mode control switch to accomplish the change.

Cheers
DD

 

Here's a good XJS A/C write-up


XJ-S Air Conditioner & Heater

 

Hi Guys.. Just found this;
So. For us guys in the warmer climates (ie DownUnder), I presume that to get normal outside (un-conditioned) into the cabin, all we would have to do is put a switch into that line that goes to the control module.
Has anyone done this or know which wire to put the switch into?
Regards, Rod.

 

If you have the Delanair MkII system....with an '86 you should.... here are a couple of "fresh air" mods:

Another Series III Climate Control Modification

Modifications to Climate Control

These were written for the Ser III sedan but the systems are the same.

Cheers
DD

 

Thanks Doug for those links. That is exactly what I was after.
Regards, Rod.