The Stovebolt Site Forums The Shop Area The Electrical Bay Fuel Gauge Question

I have replaced the sending unit, wiring and fuel gauge in my 1953 3100. The gauge does not work. I have 12 volts coming from the gauge to the sender wire with it disconnected from the sender. When I connect the sender wire to the sender, the voltage drops to .32. The voltage is present with the key on or off. How do you "properly ground" the gauge?

What kind of gauge is it?

I had a similar problem With a replacement gauge and had to clean the paint off the inside of the cluster for a good ground.

Pic

the sender IS the ground, the gauge gets + only .... if you have 12V showing at the [disconnected] sender wire to ground with the key off, you've wired something wrong - gauge power comes from the ignition switch so there should be no power there until you turn the key on

the way it works is the gauge gets a variable resistance to ground as the float moves, changing the current thru the gauge to move the needle .... look at your wiring diagram and recheck your wiring job .... also check the sender itself with your ohmmeter to see if the resistance varies from about 0-30 ohms as you move the float arm and make sure the tank is grounded so the sender is getting a good ground

Bill

I think you're saying you have 12 volts at the sender terminal of the guage with the sender wire disconnected? If so, that's probably a good reading but doesn't really prove where the trouble is. With the sender wire disconnected from the guage and the key on - what does the guage read? It should swing over to the Full mark. If it doesn't, check your ground at the guage cluster as DADS50 suggests, if that doesn't cause the guage to swing to Full with the sender wire disconnected, you've got a bad guage.

Ok..here is what I have. With my wiring issue corrected, I have 12 volts to sender on tank with key on and 0 volts with key off. The tank is full, but the new gauge reads empty. With the sender wire disconnected, the new gauge still reads empty. I get 0 to 32 ohms on the sender from E to F. I will check the ground at the gauge tomorrow. If that is good, then I guess I got a bad gauge...is that correct?

Power goes from the fuse board (or whatever you have) to the gauge. Then that power goes through the sending unit, to the ground.

So the order goes-

12v power --> gauge --> sending unit --> ground

I've got a new gauge in and during installation of the gauge I noticed a small piece of cardboard like matierial between the back of the gauge and the screws holding the gauge on the cluster. The material was brittle and broke to pieces as I removed it. The same piece of material is on the back of the Ammeter. Does this material serve a purpose and/or should I replace it with something?

yes, it serves a purpose - to prevent the terminals from shorting to the case, you should definitely replace it

Bill

What could I use? Would a piece of rubber work? Cardboard?

rubber might work if you got a piece of very thin neoprene .... or cereal box cardboard .... or the thin plastic like used in notebooks or photo albums

Bill

I would use nylon washers. Good strength and insulation

Dan Bentler

the original insulators, at least on the 55-59 trucks, were designed to also prevent shorting the wire connectors to the case or each other, it covers a large part of the gauge back and has a 'wrinkle' that stands between the terminals

Bill

I'll give the nylon washers a try. I have a new gauge...should there be continuity between the terminals? I have no continuity.

AD should be the same. With a little red tag on one terminal

...pic...

...pic...

LMC and others sell a insulator kit with that tag

Or just make your own as suggested above
Captain Crunch would work well

well 'father knows best'

note the red tag warns 'if hot wire touches, sender will be damaged'

Bill

What about continuity between the terminals. Should there be continuity? Without continuity between terminals, how would power get from ignition through gauge to sender?

Yes there should be continuity, or as you stated the sending unit would not get power, and the gauge wouldn't do anything

The gauge doesn't work installed in the cluster...with my multimeter on the audible setting I get no sound across the terminals. With the meter on the ohms setting, I get 196 across the terminals. I have twelve volts going in the gauge. With the sender wire disconnected, I get nothing on the gauge. Does this mean I have a bad gauge?

There are two coils in the gauge. Nne coil is powered by the supply and is grounded through the instrument frame. The other coil is connected to the sender. With the gauge out of the dash, you should be able to apply input power and ground the frame and the gauge shoudl read full.

Ok...I suppplied power to one terminal and grounded the frame of the gauge....still empty.

the gauge grounds in the back, not the frame of the gauge
...pic...
in that pic you see a matal plate with a gob of solder. That plate need to be grounded for the gauge to work.
when installed, it grounds to the gauge cluster.

Is that the style gauge you have?

Since this happened with two gauges, why not try this on the old gauge while it is out of the dash. With nothing attached to the sender post and power and frame ground applied, it should read full. Grounding the sender post should create a reading of empty.

yes...I have this still gauge. I have applied 12 volts to power terminal and grounded small area with solder...still reads E.

I performed all of the testing suggested and never get anything but E.

If you look at the picture supplied by Dads50, you can take an ohm meter and measure between the supply post and the ground plate. You should get a reading, probably around 30 ohms. If that is the case then applying power across there thsould cause the meter to move.

Between power terminal and ground plate...on the first "new" gauge I get a reading of 296 ohms and on the second "new" gauge I get a reading of 0 ohms.

I would think that there is something wrong in both cases. The second case sounds like it is shorted.

I sent both gauges back today...I guess I'll try another supplier.