Let's see if one of you chaps has the magic answer. In my XJ40 1988, all operation of the heating/air conditioning has ceased. The control panel does nothing. Nothing clicks or lights up, the fanms don't fan and the clutch doesn't. That suggests an electrical problem, you'll doubtless agree. I previously had replaced the microswitch. Anyway, have now stripped down the centre console and removed the control unit and unlidded it. The microswitch tests OK. All the diodes test OK (in circuit). All the resistors test OK (in circuit). That disappointed me because the Haynes darkly talks about "no action at all, send for the special Jaguar resistor" but does not tell you which one or the value. Anyway, they all test OK per the colour codes. Any other ideas, please?
Alan