109 fuel sender wiring

bill.hiscock · Apr 27, 2022

Hi all,

Trying to diagnose a faulty (reading zero) fuel gauge and thought I’d first check the wiring.
Can anyone confirm that the wires are in-fact on the correct terminals?
There after, I’ll look to pull the float and check it’s physical operation.

Many thanks.

Colthebrummie · Apr 28, 2022

Thats not quite the same as my 109, I have one wire going to the guage via a power source and a wire from a spade terminal fitted directly the the sender body going to earth. Both of yours seem to be insulated from the sender. If there is a dodgy earth, the gauge will read zero. Try connecting a good earth to that green wire and see if the gauge moves.

Col

Colthebrummie · Apr 28, 2022

Replacement senders dont seem to be very good quality, Ive replaced mine twice and still cant get an accurate reading. The latest one shows nearly zero with a full tank, then goes up as the fuel is used until the tank is about half full, the gauge reads over half a tank then it goes down again as more fuel is used. I just the trip on the odometer now to judge the tank level.

Co!

marjon · Apr 28, 2022

Have you put a meter to check a resistance across the 2 terminals (with wires removed) then put more fuel in/out and see it if changes.

I dont know what you should get but if its not a dead short and it changes then I would say look elsewhere first.

J

bill.hiscock · Apr 28, 2022

Earthing the green and black wire results in the gauge moving up.
Should it infact be connected to the non insulated terminal?

Colthebrummie · Apr 28, 2022

bill.hiscock said:
Earthing the green and black wire results in the gauge moving up.
Should it infact be connected to the non insulated terminal?

Its hard to say which of those two is the earth, logically, it will be the green. Clean the metal part of the sender back to bare metal and earth that.

Col

Shippers · Apr 28, 2022

Does the vehicle have a low fuel light in the dash if so neither are negative wires as it will use sender body connection to tank as negative supply...remove instrument cluster and check wire colour to fuel guage from sender and work back using a dmm...

bill.hiscock · Apr 29, 2022

Shippers said:
Does the vehicle have a low fuel light in the dash if so neither are negative wires as it will use sender body connection to tank as negative supply...remove instrument cluster and check wire colour to fuel guage from sender and work back using a dmm...

No low fuel light on the dash. Just the single green with black tracer going from the gauge out to the sender.

bill.hiscock · Apr 29, 2022

bill.hiscock said:
No low fuel light on the dash. Just the single green with black tracer going from the gauge out to the sender.

Borrowed from another post but may be handy for people.

ExMil109 · Apr 30, 2022

The senders on diesel models have two insulated terminals - one for the gauge and one for the warning light. Some senders also have an non-insulated earth terminal. The black wire would go to that earth terminal on the sender, but yours doesn't have one, so maybe a previous owner just connected it to the warning light terminal? It's harmless to earth the warning light terminal, but it ain't going to make the gauge work any better...
If the gauge works when you earth the green wire then it's likely the sender is faulty. But as Col said, it's worth earthing the sender body to see if that helps.

109 fuel sender wiring

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