The non air con cars have the air con switch behind the extended LCD display panel on the PCB together with the miniature LED. The air con & non air con panels have the same number of wires to the plug. Changing the LCD display for the short one and fitting the air con button physically works but when plugged in it doesn't work electrically.
Has anyone else tried this and solved the problem?

The cars without heated front screen don't have the switch on the PCB.

 

X300 was offered sans air conditioning?!?

 

In Europe, yes. Last Jaguar to do so I believe. I know for certain XJ40's were offered without AC. In the parts book there is an AC retrofit kit, now NLA.

 

I don't understand what your problem is. You have a car without AC and want to retrofit it and change the control panel? Or you just like the look of the AC panel better than the non AC panel and want to fit it to a non AC equipped car?

The panel talks to the AC ECU through an encoded data connection, so that would explain the electrical incompatibility.

 

Apologies I didn't explain my problem correctly. All three of my cars have air con. One car has one of the three heater buttons where the the little red LED doesn't light when the switch is pressed. I found a source of brand new non air con heater panels. I bought one as it cost less than the the little easily removable switch back lighting lamps. Upon stripping this non air con unit it has the micro switch which is in line with the A/C button so I thought electrically it was the same. But it isn't! I will study the two PCBs to see if I can spot the difference.
I have swapped heater panels before without any re-programming and they work ok.
My XJR is currently fitted with a panel with a heated front screen button even though the car has never been fitted with the heated screen but it works ok.
Main reason for swapping the panel was to replace worn buttons, hot/cold buttons often wear through and look well fingered.
Worst case is I will have to de-solder one of the small red LEDs from the new panel and re-fit to the failed panel.