Wiring on 110 Defender Fuel Sender Unit

Hi. Ive just had my fuel tank replaced, and am having trouble with my fuel gauge sender unit. It was working fine before it was taken out and put back in again, but now I think the mechanic messed with the wiring in a bad way.

There is a green wire (with round plastic end piece), and a yellow wire (with a round plastic end piece) and then another wire which has the usual flat plastic connector on it. The two main wires plug into the unit okay though Im not sure in which order they should be ? But the other third wire is just hanging loose as there doesnt seem to be a connector on the sender unit for it ?

There is a round metal type protrusion from the sender unit in between the other two connections, but the spare wire I have doesnt fit it because its a square connector. Is it the earth perhaps ? Is it supposed to have a connector on the wire which slides over the round protrusion ?

Im really lost and quite annoyed because it was working fine before the mechanic messed with it. When the wires were in one configuration the fuel tank was always full (when half full), then in the other configuration its always sitting just above the red even though it should probably be IN the red. Quite confusing.

Anyway, Im hoping someone knows what Im talking about and can offer some advice.

Thanks very much.

Reply to
suibhne
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Is it diesel or petrol, and age!

Richard

Reply to
beamendsltd

Oh, sorry. Its diesel and its a 1990 110 County.

Thanks :)

Reply to
suibhne

Generally there are two wires leading to the sender unit - one is for the low-fuel light and one is for the guage.

With the ignition on - earth each of them in turn - one will light the low fuel light up and the other will send the guage to absolutely full if both wires are working through to the dashboard. If both light and guage work, then the problem is in the sender unit which is in the tank - they are cheap to replace, about £20 or so.

If one wire does not work, but other does, then suspect the guage, light, or wiring to be faulty. Find the same coloured wire behind the fuel guage as is on the sender end - disconnect it, and use a multimeter to test continuity - if it fails that, then the wire is broken somewhere. As a double test of the guage, earth the terminal you just took the wire off - guage should go right up.

If you find a wire is broken somewhere - its often easier to run a new piece than find the break because the wires do run inside the chassis (done any welding lately which could have caused the problem?)

Reply to
David J. Button

I think you'll find that the green wire you mention will be mostly green with a thin black line on it as well, if so this will be the fuel gauge wire and the other (yellow?) will be the low fuel warning lamp. The small spade connector will be black and needs connecting to earth the unit as the current passing from the gauge is very small and a bad earth can play havoc with the readings. There is a small flat tag spot welded to the tank unit to connect this earth wire and if it has dropped off due to corrosion you will have to replace it or connect to the tank somewhere else, possibly by extending the wire.

Martin

Reply to
Oily

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