Fuel Gauge/Temp gauge not working

[BC_C10]

I've searched this forum over and over and I still can't seem to figure this out.

Originally the fuel gauge was at 3 o'clock, changed the circuit board (which was melted at the fuel gauge). Figured it would be good given the damage.

It now is stuck on 7/8 of a tank.

Pink #3 feed has power, but the fuel sender terminal on the fuse panel does not.

Dash lights works/redid the ground with an eyelet

Brand new tank/sender setup

There appears to be no power at either terminal on the back of the fuel gauge?

Also the Temp gauge reads dead zero, brand new gauge from LMC.

Any thoughts?

[dmack91]

I would check that the fuel sender is working. Pull it and put a ohm meter on the sender post and the main body. As you move the float arm, it should vary from 0-90 ohms, I believe. I put a new sender in what is now my son's 68. The strap that connected the sender float resistor to then post was grounded, so IT wouldn't work when new.

[dmjlambert]

OK, to summarize: #3 terminal on the instrument cluster connector has power, but you can't get power from point 1 to point 2. You need to closely examine the printed circuit and the exposed area of copper that the connector is supposed to press against, and the exposed area of copper that the nut of the fuel gauge. Make sure you don't have any paint on the cluster connector or fuel gauge terminals/nuts. Use a multimeter and figure out what is going on with that.

[BC_C10]

Ok so looked into the circuit panel, found I was missing 2 washers on the fuel gauge posts.

Added those and bam! Working fuel gauge. Now the temp gauge moves slightly with key on but when I ground the sender wire it doesn't spike up.

Next on the list will be tracing the wire back into the truck.

Thanks for the help, it's greatly appreciated!

I'll let you know what I find out with the temp gauge

[dmjlambert]

OK good progress.
So, 3 is 12V+ power for the gauge, 7 is ground, and 6 controls the temp gauge needle. High resistance between 6 and ground is cool temperature, low resistance between 6 and ground is hot.

You could probably use an ohm meter to measure how many ohms your temperature sender gives you between ground and the center pin of the sender. Then put the sender wire on it and see if you get a similar number of ohms inside the cab at the connector while it is disconnected from the instrument cluster. Maybe your sender wire has a bad connection or high resistance. Or something wrong with way the temperature gauge is connected to the printed circuit.

Member davepl showed us this chart in this thread, it is how many ohms you get from the sender at various temperatures of the engine.