Instrument display problem

[M3333]

Hi,

I am putting my 1984 350i tasmin in for its MOT on thursday and the instrument display and dash lights have stopped working.

The battery warning light, handbrake light and oil pressure light have all stopped.
The instrument lights have stopped working but the one bulb above the heater panel still lights up when the lights are switched on.

Car has been off the road for a few years and on first start up the other day all was fine, came to it tonight and had these problems.

Have checked all fuses, seem okay. The whole lot seems earthed through the bonnet release cable, i have checked this and ran a new earth supply from the battery, still no joy.

Anybody had the same problem or can point me in the right direction? The wiring loom looks to be in good shape for the cars age.

Thanks.

[adam quantrill]

Try running an earth strap from the rear of the engine (where the earth straps bond to the hoist loop) through the bulkhead grommet to the bonnet release cable end in the cabin?

What else doesn't work - oil pressure gauge - temperature - ignition light - indicators - clock?

[M3333]

Thank Adam will give that a try.

Everything else works, indicators, horn, the lights all actually come on, its just the ones that illuminate the instruments. All gauges work etc.

I am guessing the instrument warning panel is fed by an igniton live then switched earths at the oil pressure switch and handbrake? The warning light probably cancels itself out with 12v from the alternator when running.

It has baffled me!

The light that comes on in the instrument warning display when the lights are switched on works fine (blue/purple one)

[marcus1875]

hi,
None of my dash lights work. Not wired up. Nor do i have any illumination on the clocks. Never failed an MOT. Not tested according to my tester when quized.
Marcus

[M3333]

Cheers Marcus, that is good news! I just want to get it roadworthy and worry about all the jobs to do after!

I have had a look in the steve heath 'bible' and it looks like the three lights not working are fed from a 20 amp fuse number 9. I am going to recheck everything tomorrow night. Its booked in for its MOT on Thursday at 12:30. Cant wait to drive it again!

[Wedg1e]

marcus1875 said:

hi,
None of my dash lights work. Not wired up. Nor do i have any illumination on the clocks. Never failed an MOT. Not tested according to my tester when quized.
Marcus

NONE of them? Your MOT tester might be on the blink then...

"Warning lights

As well as electronic parking brake and electronic stability control warning lights (where fitted) the MOT test will also include checks for the correct function of the following, where fitted;

Headlight main beam warning light
Electronic power steering warning light
Brake fluid level warning light
Seat belt pre-tensioner warning light"

At lest two of those will be on your Wedge Luckily we don't have to worry about the bloody airbag and ABS lights that plague so many cars.

http://www.theaa.com/motoring_advice/car-servicing...

[Wedg1e]

M3333 said:

Cheers Marcus, that is good news! I just want to get it roadworthy and worry about all the jobs to do after!

I have had a look in the steve heath 'bible' and it looks like the three lights not working are fed from a 20 amp fuse number 9. I am going to recheck everything tomorrow night. Its booked in for its MOT on Thursday at 12:30. Cant wait to drive it again!

Don't rely on the diagrams in that book - or even the ones on the car or in the manual - TVR changed stuff a lot, sometimes apparently by accident. The relay layout chart on my car is at best only 60% correct. One day, when I'm bored with the internet, I'm going to strip the relay board and reassemble it the way the diagram shows

[M3333]

Wedg1e said:

Don't rely on the diagrams in that book - or even the ones on the car or in the manual - TVR changed stuff a lot, sometimes apparently by accident. The relay layout chart on my car is at best only 60% correct. One day, when I'm bored with the internet, I'm going to strip the relay board and reassemble it the way the diagram shows

Oh joy

Have to say the relay and fuse diagram looks nothing like it does in the car and the picture shows the fuse board under the bonnet instead of the passenger footwell. Brilliant!

[Wedg1e]

marcus1875 said:

hi,
None of my dash lights work. Not wired up. Nor do i have any illumination on the clocks. Never failed an MOT. Not tested according to my tester when quized.
Marcus

From the same AA link above:

"Speedometer

The car will fail if a speedometer is not fitted, is incomplete, inoperative, has a dial glass broken/missing or cannot be illuminated."

[pasogrande]

I thought I read recently that this problem is caused by the poor quality rheostat, that controls the instrument lighting brightness; and that by turning it as far as possible in each direction, the problem usually goes away.

Wilf.

[M3333]

Thanks for that, where abouts is the dimmer switch/stat in the car as i cannot see one?

[Wedg1e]

M3333 said:

Thanks for that, where abouts is the dimmer switch/stat in the car as i cannot see one?

Early cars (TR7 steering column) had a two-position switch in the radio console, you'd struggle to see it doing much
Cars with the SD1 column have a rotary control above and behind the wiper stalk.

[Rib]

dont tell him he might have a TR7 steering column!!!! he will never hear the end of it from me lol :P

[marcus1875]

Wedg1e said:

marcus1875 said:

hi,
None of my dash lights work. Not wired up. Nor do i have any illumination on the clocks. Never failed an MOT. Not tested according to my tester when quized.
Marcus

NONE of them? Your MOT tester might be on the blink then...

"Warning lights

As well as electronic parking brake and electronic stability control warning lights (where fitted) the MOT test will also include checks for the correct function of the following, where fitted;

Headlight main beam warning light
Electronic power steering warning light
Brake fluid level warning light
Seat belt pre-tensioner warning light"

At lest two of those will be on your Wedge Luckily we don't have to worry about the bloody airbag and ABS lights that plague so many cars.

http://www.theaa.com/motoring_advice/car-servicing...

sorry, need to stop posting after an afternoon in the pub!
Not all my dash lights are unconnected, indicators and main beam work. But no others and no illumination.
i dont have an electronic parking brake nor electronic stability.
Dont have power steering, seat belt tensioner and i've never seen a brake fluid light on it either. Whats the second one i should have (got main beam)?


The car passed its first MOT in my ownership with no working speedo, and has continued to pass without illumination.

Marcus

[mrzigazaga]

marcus1875 said:

The car passed its first MOT in my ownership with no working speedo, and has continued to pass without illumination.

Thats right mate..Who needs to see where they are going and at what speed....MOT testers..What do they know?....Actually it sounds like yours is very understanding...Or Very very drunk....

[Wedg1e]

marcus1875 said:

sorry, need to stop posting after an afternoon in the pub!
Not all my dash lights are unconnected, indicators and main beam work. But no others and no illumination.
i dont have an electronic parking brake nor electronic stability.
Dont have power steering, seat belt tensioner and i've never seen a brake fluid light on it either. Whats the second one i should have (got main beam)?

The car passed its first MOT in my ownership with no working speedo, and has continued to pass without illumination.

Marcus

The handbrake warning lamp doubles up as the brake fluid level warning.

We all know that most MNOT testers turn a blind eye to some of the trivial stuff - or maybe don't know about it; the classic case being young lads who don't realise that a lot of rear-wheel drive cars have taper roller bearings in the front hubs that are supposed to have a bit of play when cold - they assume it's wear and call a fail.

[marcus1875]

I'm in the pub again

Wedg1e said:

The handbrake warning lamp doubles up as the brake fluid level warning.

I did not know that.

We all know that most MNOT testers turn a blind eye to some of the trivial stuff - or maybe don't know about it; the classic case being young lads who don't realise that a lot of rear-wheel drive cars have taper roller bearings in the front hubs that are supposed to have a bit of play when cold - they assume it's wear and call a fail.

Didn't know this either. Now i feel very silly not knowing these. Won't change my tester though, I think he's doing a splendid job! He does classics and higher end motors, so as you say, probably turns a blind eye to the more trivial (if anything in the MOT can be called trivial). I'll add dashboard wiring to my growing list.
marcus