dash lights problem on 88 Turbo

[sgrobler]

I've got a rather annoying problem with the dash lights. They stopped working completely a little while ago so I tool the binnacle off to check them. All lamps are OK and all work fine until I tighten the binnacle down! There are 4 bolts that go through the steel dash cross member to hold the binnacle down. The mating brackets on the binnacle are steel brackets screwed to a plywood frame so there does not seem to be a conducting path between the binnacle and the bolts. But when I put these bolts in, the dash lights flicker on and off. Sometime I can get 3 in with no problem and then as soon as the 4th one goes in the lights go out!

As long as I don't tighten the bolts fully I can wiggle the binnacle into a position where the lights stay on. But as soon as I tighten them up the lights go out. Bumping or pulling/pushing the binnacle can make the lights come on momentarily. Buggered if I can work out whats going on!

Bizarre!!

Anyone got an suggestions for me to try?

Thanks

Steve

[Choppa]

It's got to be something to do with an earth lead somewhere in and around the binnacle, wouldn't have a clue as to where you should start looking. Trace all the black wires back to the bullet terminals and the earthing point, give all the connecting points a clean with some sandpaper, reassemble and see if that make a difference. 

[Vulcan Grey]

I had a problem in my 89 SE where a friend turned the dimmer knob while the car was off (he was noting how the location was different than his 90 SE) and then when I later turned the car on at night, the dash lights wouldn't work, no matter how much I turned the dimmer knob.  Then they cam on when I turned on the parking or fog lights (but not with the headlights)...  And continued to work fine after that, when the headlights were used normally.  It may be something to do with those switches.

 

[sgrobler]

Thanks for the feedback. I haven't sorted it out yet.

It's really odd as the binnacle wiring is all self-contained, just two connectors, that carry all the earths etc, so its not as though it relies on the binnacle being earthed through the bolted connection.

Before this happened I noticed (for many years) that my rev counter would sometimes not work when I first started the car, but if I bumped the binnacle it would start working. Its probably all related somehow!

Steve

 

[Qavion]

I

Quote

 

had a problem in my 89 SE where a friend turned the dimmer knob while the car was off (he was noting how the location was different than his 90 SE) and then when I later turned the car on at night, the dash lights wouldn't work, no matter how much I turned the dimmer knob.  

 

I wonder if tightening the 4th bolt warps the wood or veneer on the instrument binnacle and puts pressure on the dimmer knob.

[Escape]

Could one of the bolts touch the wiring when tightened? Or perhaps crush wires between the dash and binnacle?

[sgrobler]

Thanks for those tips, I've not been able to look at it again yet, maybe this weekend.

I did look for signs of wires getting crushed, but they are all well clear of the binnacle and the bolts.

Looks like it will have to be disconnected again (getting the speedo cable back is the painful bit).

[sgrobler]

Well dash lights are working again. Got no idea why! Pulled the binnacle off and re-fitted multiple times. Light always worked fin as long as binnacle was not bolted down. It often happened that as soon as I started to screw in the last bolt, lights would go out. I did accidentally pull out one of the lamps in the speedo - whenever I plugged it in, the lights went out. I found that the positive wire was going to its metal casing  - I think the positive should be to the centre-pin. Maybe the live was shorting through to ground via the speedo casing. Anyway the lamp glass was loose too, so I've left that lamp out waiting on a replacement lamp to arrive from UK.