Jaguar Repair: Dashboard lights, dashboard lights, fuse panel

Question
QUESTION: Hi Howard,

Recently my dashboard lights stopped working.  I've checked all of the fuses and they are all ok.  The turn signals work and all of the dummy lights work as well.  What can you suggest?

Blake

ANSWER: Yes Blake, I have a suggestion. Tell me what kind of Jaguar this is.
Howard

---------- FOLLOW-UP ----------

QUESTION: Sorry about that, its an 1985 XJ6 VDP.  

Thanks

Answer
Hi Blake,
All panel lights are powered by one fuse. (fuse #8 in the main fuse panel) The glove box light is powered directly off of that fuse as is the cigar lighter light. All other dash lights run from that #8 fuse to the dash rheostat then on to each individual light including the the fiber optic light that lights up the heater controls, ignition switch and light switch.

If this car came to me in the shop, I would first turn the lights on and open the glove box to confirm that the #8 fuse is supplying current. If the light is off, I would then test the fuse while still in the fuse box with a test light on both ends of the fuse. If the glove box light was on, I would remove the rheostat and test the red w/blue tracer wire for power from the #8 fuse. If power is on that wire, I would test the red w/white wire from the rheostat to see if power is going through the rheostat. If power is going out of the rheostat, I would check the bulbs. It is unlikely all dash light bulbs can burn out at once but it does happen when you have a alternator / regulator fault that goes into "full field" and over charges which usually burns all dash lights out first.

I hope this helps, let me know.
Howard