The dashboard and all the interior lights of my 85 XJ6 are off except park break which is permanently on.
The tail lights are also off.
how do I fix this?

 

With any lighting faults begin by checking the bulbs and fuses.. And 'checking' includes cleaning away any corrosion on the contacts.

Do you have a 12v test light? it would be helpful.

You've mentioned several different lighting circuits so you may have to diagnose them individually. Some of them might share earthing/grounding points, though...so cleaning the grounds might be the fix.

Do you have the S57 wiring guide? It would be very useful here

Cheers
DD

 

Thanks DD,
i did some corrosion cleaning around the fuses at the driver side and the lights are working now.

But, when I switched on the high beam, it's only the driver side that works whiles the passenger side high and low beam goes off bit when switch to low beam, the two sides low beam works fine.

Where and what do I check to fix the passenger side problem on the low and high beam when high beam is switched?

 

There is a separate fuse box for the headlamps and electric cooling fan on the left side inner wing in the engine bay. Start by checking for bad fuses and poor connections there.

 

Andy, i did the check that but seems bad connection as suggested but still problem exist, I will test the fuses to check.

Interesting side of your submission is, how do connect electric modern car fan if I want to change the existing fan on the engine?

 

Your car should already have an auxiliary electric cooling fan in front of the air con condenser.
Best to continue this aspect of the discussion in your other thread about over-heating

 

I cleaned all the bullet connectors between fuse box and lights and the earths - that worked