I'm having trouble with my instrument panel and tail lights (and side marker lights) not working on my 1990 XJ/6 (40) Sovereign. The problem is intermittent but getting worse. They rarely come on anymore. No amount of jiggling the dash switch seems to make a difference. But if they are on and you turn the switch off, they probably will not come on again. I switched out the under glove box side marker relay to no effect. As a matter of fact, I pulled it out while the dash and tail lights were ON, the panel lights stayed on - the tail lights went out. Put it back in, turned the master switch off/on - then no lights. Pulled it back out - no lights. The bulb circuit warning light is also on, but I think it remains on even when the lights are working - I cannot double check this at the moment as I cannot get the lights (again - tail lights and panel lights, Headlights work fine) to come on again. I have found some related posts up on this forum, but have not found the relevant one yet.

Could any one please steer me in the right direction?

IroqRT

 

Hi IroqRT,

If you don't have the 1990 XJ Electrical Guide you can download it here:

http://www.jagrepair.com/images/Elec...Electrical.pdf

Off the top of my head, one possibility would be corrosion on an electrical connector at the CPU (called the Central Microprocessor in the Electrical Guide). The CPU is involved in most lighting functions and corrosion on one of its electrical connectors is a known issue due to water ingress. The water comes either from a plugged duckbill drain on the windshield undercowl (near the windshield wiper motor), or plugged A/C drains allowing condensation from the evaporator to pool and slosh from the climate control unit in the center of the dash onto the CPU.

Another likely suspect would be the Auxiliary / Side Light Relay, but is sounds as though you have already tried switching it out with a known working relay.

The schematics in the Electrical Guide will help you trace common points in the circuits that could effect both the instrument panel lighting and the tail & side marker lamps.

Please keep us informed.

Cheers,

Don

 

Thanks Don for that wiring diagram. By those diagrams I found that the only common switch shared by all tail, marker, and dash lights was the master lighting switch on the steering column. I disassembled the switch and found a heavily corroded circuit board inside. Wiggling this board causes the lights to flash on and off so there is an obvious bad connection. I took the board out and cleaned it but could not further isolate the problem or stabilize the connection. So I ordered used parts off ebay to replace the switch and board. I was unable to locate new parts online - where do I go to find new parts? My closest dealer is a 5hr drive away.

 

Check our sponsors for new parts. I have had good to excellent luck with both SNG Barrats and XKS unlimited. For the more "generic" parts like brakes, tune-up, and suspension Rock Auto is "usually" least expensive and often has choices of items. Bear in mind, it pays to compare as prices are rarely the same between suppliers. Also, Jaguar Heritage has the actual parts blow-ups with part numbers in most cases which you can use for reference. Good Luck