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flananuts February 2nd, 2014 08:12 PM

3 spade 110 diesel fuel sender with only two wires
I'm trying to solve a fuel gauge issue and would love a little help. The fuel sender has 3 spade connections vertically with what looks to be a fuel return line to the left. I have identified the black/green wire that is supposed to connect to the sender and the other I suppose is to the ground. Right now the green/black is in the top spade and the other wire is the bottom with the middle spade is empty. Is this right?

I don't think I have a low fuel light on the 84 110 RHD but then again I've only had it for a week now.

Appreciate the help.

Ash February 2nd, 2014 09:10 PM

-The top spade has a green/brown wire that is the signal for your fuel gauge.
-The middle spade has a +12v white wire that is the 'line in' for the sending unit.
-The bottom spade has a black wire that is grounded.

I could be mistaken, but I don't believe your truck should have a low fuel warning circuit.

flananuts February 3rd, 2014 03:36 PM

Ash, thanks for this, with no white wire plugged into the middle, that may be why I don't have a working gauge. Does that piggyback off the fuel pump or it is part of the wires for the gauge. My gauge wire is the green/brown and black.

Really appreciate your help.

Ash February 3rd, 2014 04:56 PM

Not a problem!

The lack of a 12v feed into the middle spade will definitely keep your gauge from working. The power provided by the white wire travels through the sending unit, which is just a big resistor, and out to the gauge via the green wire. The current to the green wire varies based on the position of the float, which is what sets the position of the needle on the fuel gauge.

Anyways, according to my diagram the wire traces all the way back to the fuse panel, which means it's going to be a part of your chassis harness. In theory you could jump a 12v feed from the fuel pump down to the sending unit, however if there is a lack of voltage I imagine it'd cause the gauge to read improperly. I could be wrong though.

If you don't have any trailer wiring on the truck there ought to be a handful of unused wires in your chassis harness near the back right corner of the tub. I'd find one that is switched off the ignition and make an extension that leads to the sending unit. Good luck!


flananuts February 3rd, 2014 06:16 PM

Thanks, I'm going to poke around and see if I can in fact the missing white wire that the PO forgot to reconnect.

Ash February 3rd, 2014 06:33 PM

Oh I should mention...

The 110 in my driveway has a white wire, however the diagram is a little confusing. The wire in the illustration has no color indication, but it T's into to a brown wire that leads from the starter solenoid to the fuse panel. Couldn't hurt to look for a brown wire down by the tank as well.


Red90 February 3rd, 2014 07:25 PM

One is ground, one is the sender and one is a low fuel. You can figure out which with a meter. There will be resistance from the sender to the ground that will vary with level. The low fuel will be open full and closed empty. You can just trial different connections. You won't hurt anything.

Ash February 3rd, 2014 10:21 PM

I stand corrected! My diagram is a little worn out and the wire appeared to terminate. Guess my understanding was off.

Matthew, if you look at the diagram I sent over you can trace the white/slate wire back from number 34. It fades out but if you keep following it you'll see that it picks back up on the wire that leads from the middle terminal on the sender.


flananuts February 4th, 2014 05:57 AM

Another question in order to rule out electrical/gauge first, should I be able to detect 12v from either of the spade connections? Should I have three wires connected or only two? If I use my multimeter on the sender terminals should I read some resistance(which I think yes based on other threads)? What about the black/green wire to the gauge? Should I read any voltage or resistance?

Appreciate all the help.

Red90 February 4th, 2014 06:40 AM

The wire from the gauge should read 12V (with the ignition on). The other wire should be connected to ground.

There should be resistance between the ground and level connectors on the sender. Around 300 Ohms empty, 15 Ohms full. The low fuel will read 0 empty and infinite full. It switches at around 1/4 tank.

flananuts February 4th, 2014 07:15 AM

Thanks John, that helps immensely. My gauge wire was reading 0V when I tested it. I'll pull the dash and make sure that i have voltage at the gauge first, then inspect the plastic plug prior to the spades.

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