I recently bought a Jaguar xj6 1991 and I have no backlight on my Dash I've changed fuses and played with the dimmer knob the miles display changes when I play with the dimmer knob but I still get no lights in my gauges all the warning lights and gauges work there's just no way to see my speedometer and RPMs at night

 

Hi Cedric,

The dimmer modules are known to fail, but the fact that yours seems to control the odometer may mean it is working. The dimmer has multiple outputs, to feed the instrument cluster (IC), the fascia switch pack, the center console, the climate control panel, etc. If I recall correctly, there are eight bulbs on the back of the instrument cluster that provide backlight for the speedometer, tachometer and smaller gauges. The bulbs do fail eventually, but it is unlikely that all eight of yours have failed simultaneously.

The Central Microprocessor (CPU) is involved with interior and instrument lighting, and a known problem is water on the electrical connectors or water ingress into the module, due to clogged AC drains below the evaporator that run down either side of the transmission tunnel. When these drains become clogged with deteriorated foam insulation from inside the climate control unit, water pools below the evaporator and sloshes onto the CPU when making left-hand turns.

Other suspects would be the various electrical connectors at the dimmer module, the back of the instrument cluster (4 connectors), the fascia switch pack, etc. See the wiring diagram on pdf page 29 of the Electrical Guide, which you can download here:

Jaguar XJ40 Electrical Guide 1991

Cheers,

Don

 

as it turns out after doing some looking around I found a toggle switch where one of the screws would be to take off the bottom panel under the steering wheel that toggle switch turned out to be my dash lights so thank you everybody for your help and the knowledge the PDF is awesome

 

Another new owner bitten by the vagaries of a zealous PO twit . . . Cedric, welcome to the club. Thank your lucky stars your previous owner did NOT resort to the solutions adopted by a PO of my otherwise beautiful Solent Blue XJ40 Sovereign . . . snip off any wire associated with any gremlin that surfaced until, after some years, the car finally gave up. I bought it for parts, paid nothing, but it grieves me to see such a beauty reduced to its knees.

Yours sounds like a happy outcome.

Cheers,

Ken

 

Ive just fixed a long term lack of dash lights by replacing the dimmer switch