Weird fuel gauge issue with aftermarket fuel cell

[dubseven]

I built an aluminum fuel cell for my 68 D200. I used this sender: http://www.summitracing.com/parts/vdo-221012/overview/

The gauge is stuck a HAIR above E. I got a gauge from another truck, and it worked great when i plugged it in to test it, outside the cluster. However, the temp gauge went to the middle with the truck cold. Once I bolt the gauge into the cluster, same issue, but the temp gauge goes back to normal.

if I take the sender wire off and ground it to the frame, the gauge pegs past F.

[wally426ci]

Maybe something is crossed with ground? Make sure you ground your gauge cluster (wire) to the fuse block mount.

[dubseven]

I ran a new ground, didnt fix anything. There is .2-.3ohm of resistance from cluster to chassis

[PwrWgnWalt]

You may know all this already... And don't know that any of this will help:

The VDO sender is built to provide 73 Ohms resistance when the tank is Empty, 10 Ohms when Full.

If you have the standard gauges, I believe your fuel gauge will have an internal voltage limiter, to produce 5 volts at the gauge (the round HD gauges have an external voltage limiter). If not working right, may impact Temp and Fuel gauges. Should read a fluctuating 7 volts (ignition in 'run' position) between Temp gauge "A" post and ground.

Must not connect 12 volts to any terminal other than the Ignition terminal of the fuel gauge (the one with the buss bar), or damage to gauge and/or limiter may result. (This is where the red wire w/female spade connects)

On Fuel gauge (w/internal voltage limiter):
A = Voltage Limiter output (goes to Temp gauge post 'A')
I = Voltage Limiter input (power source, from Ignition/Battery)
S = "signal", fuel sender connection (from tank)

* The gas tank must also be well grounded, including the top of the sender to the tank.

Wonder if all the instrument cluster wires are connected properly? If it works unmounted, but doesn't when mounted, seems it is in the connections somewhere.

Anyway, hope you get the gremlin figured out!
-Walt

[Hobcobble]

John