Wiring woes. Losing the will to live.

I'm in the process of wiring the 90 back together (1987). When I bought it no gauges or lights worked. I've managed to get most of the lights working along with things like interior clock and 12v cigarette lighter. I've just got a few small issues left to sort which I'm stuck with.

Firstly the dash boards light will not light up when you turn the lights on. They've been on before (about a week ago) but they're not now. Now here where it gets strange. I accidentally connected the fag lighter wires to the rear wash wipe, earth, red/white and green. And the dash lights came on permanently and wouldn't turn off. I figured if I send a live down the red/white which is fag Light illumination then they turn on. So why can't I get them on with the actual sidelight switch.

Secondly, the fuel gauge didn't work, I've removed the sender, had a multimeter onto it and the sender works as it should, ran the wires to behind the engine but I've no idea what colours or which plug it plugs onto? It's had some hit and miss wiring but surely it plugs into something! I've got a selection of green, white, Brown, purple/orange, yellow/white all spare?

Thanks in advance
Ash

This is my 86 before stripdown.
Feed from the lights to dash lights need looking at, get the multimeter out.

You will have reverse switch and diff lock switch for the others.

Gmacz said:

This is my 86 before stripdown.
Feed from the lights to dash lights need looking at, get the multimeter out.

Click to expand...

My wires from the sender are fine. It's where they plug into the wiring loom which is the issue. I've nearly thrown the multimeter through the window!

Reverse light switch works and so does diff lock

I've just found on a wiring diagram online a panel illumination switch? What's this? Because I'm sure I don't have one

Was that military only??

Ash2304 said:

I've just found on a wiring diagram online a panel illumination switch? What's this? Because I'm sure I don't have one

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Do you have a switch on the row of 3 near the drivers door that does the interior light? this also does the dash lights on some older models...

And it is three position
1 interior lamp
2 all off
3 dash lights.

As per the above, you should have a switch in the panel at your right knee. It controls the interior light and allows you to switch off the dash gauges, for driving offroad at night.

White/slate is the low fuel warning light, green black is the fuel sender. Look for these colours in the plugs on the engine side of the loom - where it comes out of the bulkhead.

MsFire said:

Do you have a switch on the row of 3 near the drivers door that does the interior light? this also does the dash lights on some older models...
View attachment 122165

Click to expand...

ive got one of them pressed it once and could not understand why I had no lights on the binnacle working

Not sure if these are any use for you, can't find the full diagram
I know your woes though haha goodluck

Thanks for the replies! Tonight's saw a little more progress. It didn't have one of them switches in when I bought it but I bought a new bulkhead which came with one. But I have no wiring/plug for one so I won't be wiring that in. I can't understand why I don't have a red/white behind the clocks going live when I turn the lights on, I think I'm going to have to join them to another one elsewhere?

With regards to the sender, I've managed to find the correct wire for the gauge and plugged it in. However the fuel gauge doesn't behave normally. It goes right to the top and doesn't come less than half way when I move the sender up and down. If I swap the wires around it doesn't really alter it. Sometimes it behaves the opposite to what it should do. The gauge isn't faulty as it goes from empty to full when a live is connected so is it likely to be the sender itself? I have tested with a multimeter from empty to full and the voltage increases as i would expect. So am I missing something?

The red/white behind the clocks is joined to a red from the light switch.

Me again. Hoping people can help with some new issues.

Fuel gauge.... I've got a new sender, ran a new wire direct to the gauge itself and still doesn't work as it should. On 'empty' it says it's around 3/4 full. And then moves off the scale when it increases. I've tried another second hand gauge which is exactly the same. I've also put the wires onto the back of the temp gauge and it does the same thing, albeit starting at around half a tank not 3/4.

Second issue is when putting main beam(high beam) on, the blue symbol doesn't light on the dash. I've swapped bulbs and holders for one that works and still doesn't work.

Any ideas please

Thanks

Post not making much sense, temp gauge/ half tank ?

I've connected the fuel wires to the temperature gauge to see if I can get the temperature gauge to act as a fuel gauge so a faulty fuel gauge can be ruled out. However it behaves in the exact same way, but when the fuel tank is empty it shows half full. Where as if I do the exact same but connected to the fuel gauge itself it shows 3/4 full when it should read empty.

Fuel light works perfect as it should.

I know if you put in td5 guages on a 300tdi you need a diff sender and either a resistor or rewire through the speedo to make it work, maybe yours is a similar compatability issue?
Full beam warning light wise check that there is 12V to the bulb when the switch is on and check the earth from the bulb might just be a wiring fault could be at the bulb or switch or anywhere inbetween
Multimeter is best friend
Also does the guage read empty when disconnected? Maybe the internals are not set to 0 if not
Also the fuel guages are compensated through the speedo aswell I think to account for sloshing in corners dampers the current to stop it bobbing at every bend

alexc2701 said:

I know if you put in td5 guages on a 300tdi you need a diff sender and either a resistor or rewire through the speedo to make it work, maybe yours is a similar compatability issue?
Full beam warning light wise check that there is 12V to the bulb when the switch is on and check the earth from the bulb might just be a wiring fault could be at the bulb or switch or anywhere inbetween
Multimeter is best friend
Also does the guage read empty when disconnected? Maybe the internals are not set to 0 if not

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Ah I see. Well mine would of been a 2.5 turbo diesel and it has had a 200tdi fitted at some point down the line. That would make sense if the gauge should be reading zero but it's reading 3/4 full, a resistor of some kind would sort that. But how do I work out what size resistor I need

Yeah I've got a multimeter, it's helped basically rewire all of the lights and get 99% of things working. The gauge does read zero when it's disconnected yes. And then full when a 12v supply is put to it so I'm pretty sure it's working as it should.

Ill just have to do some fault finding with the bulb issue I think.

Cheers for the reply

Ash2304 said:

Ah I see. Well mine would of been a 2.5 turbo diesel and it has had a 200tdi fitted at some point down the line. That would make sense if the gauge should be reading zero but it's reading 3/4 full, a resistor of some kind would sort that. But how do I work out what size resistor I need

Yeah I've got a multimeter, it's helped basically rewire all of the lights and get 99% of things working. The gauge does read zero when it's disconnected yes. And then full when a 12v supply is put to it so I'm pretty sure it's working as it should.

Ill just have to do some fault finding with the bulb issue I think.

Cheers for the reply

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You could either source a matching sender and guage fit a custom vdo guage or trial diffirent resistors. If yours is wired direct to the guage from sender I believe it is incorrect. There has to be a damper between the guage and the sender or it will bob up and down when you go around corners. I know on the td5 set this is worked through the speedo. If you check the diagram that matches to your guages guessing tdi set? ?? I think they'll need something similar which will probably make it settle at 0 for 0. If you can connect the sender wire to the correct pin on the instrument cluster loom and reconnect the guage wiring from that it might work? Don't know how your setup is to say if it's all custom wired you'll need to sort out. A plain resistor won't work on own like for the temp sender tho cos bobbing