Fuel sender unit voltage/wiring

[digitalDougie]

I've not had my Bongo for long, the fuel gauge didn't work when I got it. I managed to get to the top of the sender unit today and thought it was going to be an easy fix after reading the forum posts about bad earths and manky connections. However, although the connections were covered in muck, cleaning them up didn't do anything.

After checking the wiring I found the voltage to be only 6.6 volts, the earth wire is fine though. Having a look at the wiring diagrams, I reckong the wiring comes out the dash cluster and goes to X-20 on the block diagram linked to below.

Can someone tell me what X-20 is please, is it a plug? If so, how do I identify it?

Cheers

Dougie

[g8dhe]

The voltage sounds about correct, the gauge is fed the +12v, the gauge is then connected to the top end of the variable resistor down in the tank, the lower end of which is earthed.
X20 is a large loom connector normally tight to the chassis, however it doesn't carry the that signal in all types its in X22 in other versions but if there is 6.6v on the tank end then its connected thru to the gauge itself. However there are variations depending on year and fuel type.
Does the gauge indicate anything ? Is it far left or far right on the display or what level is it indicating ?

[digitalDougie]

Thanks for that, I thought there would be 12v on the end of the +ve wire, I can understand a drop when it goes through the variable resistor. This is a 2.5 Diesel, 'P' 1997.

The gauge is as far to the left as it will go. It's covering the 'E' symbol. No movement at all when 12v is put on the wire...

Dougie

[g8dhe]

Sounds odd, might actually be a faulty gauge, but try earthing the wire from the gauge to the variable resistor that should cause full scale deflection (to the right) ? Below is the diagram for 1997/11 prior to that its as you showed.

The normal problem on the diesel is that the earth for the variable resistor comes via a tag board on the top of the tank and this fails, so earthing the tank restores the earth, might be worth putting a new earth to the tank itself and see what happens?

The gauge has a locking function, so that when the Ignition is Off it locks the display position so you can always see what should be in the tank, I wonder if that has failed, its why the gauge has three wires +12v, signal and then an earth connection the +12v and earth release the lock when power is on.

[digitalDougie]

Thanks again Geoff. I'll try that next, I also checked the continuity for the +ve at X20, it's also 6.6v on both sides of it.

[digitalDougie]

Earthing the tank worked @g8dhe thanks again, appreciate the advice.

Dougie

[g8dhe]

Excellent its by far the most common problem!