Lost all instruments suddenly in my 85 xj6

First the dash lights went out completely, next day all the instruments and trip computer died. Outside lights still work and also the warning lamps.
Could the problem be the voltage stabilizers?

Simple things first…
Check fuses and grounds

I checked all the fuses and they are all good.
I noticed 2 voltage stabilizers attached to the right side of the dash, behind the plastic cover. They are very rusty. I was wondering if those both failed, but they wouldn’t put out all the instrument lights would they?

They shouldn’t (do I know), but maybe the whole panel lost all its grounding and thus neither instrument lighting (from the switch) nor instruments work?
Also, fuses looking good don’t mean anything. You probably know that. But as the power for the lights is from the switch via the rheostat and the instruments have their signals from elsewhere the whole panel is the common thing to ground first. The stabilizers shouldn’t affect the light. But they need ground.

I ‘lost’ my wipers yesterday, the fuse was good BUT dirty contacts, just removing the fuse and re-inserting started them up again. Time to get in with some light emery paper.

Your 1985 XJ6 doesn’t have any voltage stabilizers. What you probably found were the bulb check units for some of the exterior lighting.

Have you tried turning your panel lighting rheostat from full off to full on several times? Perhaps the rheostat hasn’t been used in a while and has built up some corrosion?

A faulty rheostat might explain your instrument panel lighting problems.


Paul, the lights are one problem but the instruments have given up soon after. Dusting off the rheostat can help with dim or even dark lights, my feeling is that this is not it. Aren’t the BFU units where the ECU is?
What is there instead of stabilizer(s)? Is it the internal units in the gauges that do that?

Thanks guys for all the responses. I did fiddle with the rheo knob and have them fail in the past. I’ve completely removed them from 2 of my cars already. Why would anyone want the dash lights any dimmer than they already are.
I was asking about the VS’s because my TR6 uses one for the fuel and water temp gauges and if bad or miss-wired, neither instrument will work.
I hear you about the grounds and corrosion, been a lot of rain hear lately and the roads are terrible probably causing things to get loose along with my fillings.
I will check all the grounds this weekend. Rust and oxidation never sleep.

Maybe fuse the lights though. I have dimmed them before but that dimmer is an insult. Good luck on the grounds; it might help to ground the plate to the chassis just to find out before a full teardown. I am curious about the voltage regulators, but I couldn’t pinpoint their location from memory so Paul must be right. I would like to know how the voltage gets stabilized nevertheless; surely he knows.

There are no voltage stabilizers on the 85, Baws - let alone 2…

Some instruments are mounted, and grounded, to a separate metal subframe - which in turn is grounded by a separate wire. As you had two ‘separate’ failures; you may have two separate faults to pursue…?

xj6 85 Sov Europe (UK/NZ)

Thank you Frank for clarifying the voltage stabilizer question, those 2 devices on the right side of the dash must indeed be bulb failure units. So much for that red herring.

I always believed the problem with the lights and gauge functions were not being caused by the same thing, just coincidental that they occured one right after the other.

I did trace the gauge issue to the ignition switch, fiddling around with the key in the switch brought the instruments back to life and using the spare key, which is not nearly so worn worked a treat this morning on the way into work. Until I get the dash lights working again and I still suspect the rheostat, a small battery powered LED light bar will have to do. When I get that resolved I will report back.