Fuel Gauge Dilemma - diagnosis help please

[bdgregory]

I have a 2004 20V and the fuel gauge will not register correctly (there is a very minor deflection to barely above "E"). I tested the sender - it's fine. I tested the gauge itself, it works fine. The other gauges in the cluster work fine (this is the Faria multi gauge unit). Continuity from the gauge to the sender is fine.

Is there anything else I can do/check?

thanks in advance!

Further info: I have used 2 other gauges - same problem. The gauge test - short to ground - gauge reads "F"; short to B+, gauge reads "E". Sender test - Resistance at Full - ~30ohms, Resistance at Empty - ~ 230 ohms. Oh, and the tank is at ~ half full now, the gauge did the same thing when it was full.

[UNSTUCK]

What does "short to B+" mean?

Redo your gauge test: remove the gauge wire from the sender. Open circuit will read F or E on the gauge. Grounded (shorted) will read the opposite. Sending 12v down that wire to the gauge would do weird things to it.

[boatwakes]

Replace the sender. How did you test the sender?

Also, ALL fuel senders are an indexed 5 bolt pattern which means they will ONLY line up to the bolt pattern in the tank ONE WAY. We mark the old unit and compare to new before installation. Good luck!

[bdgregory]

What does "short to B+" mean?

Redo your gauge test: remove the gauge wire from the sender. Open circuit will read F or E on the gauge. Grounded (shorted) will read the opposite. Sending 12v down that wire to the gauge would do weird things to it.

thanks for the reply, (I think) your method is what I did. "B+" is the 12V from the ignition. I removed the signal cable at the gauge, not the sender. On this model giving ~12V to the ground terminal on the gauge will read Full. 12V to the signal terminal reads Empty. This is what it did.

[bdgregory]

Replace the sender. How did you test the sender?

Also, ALL fuel senders are an indexed 5 bolt pattern which means they will ONLY line up to the bolt pattern in the tank ONE WAY. We mark the old unit and compare to new before installation. Good luck!

thanks for the reply. I removed the sender and connected a meter across the terminals. I slid the float and noted the resistance changes at all points. The F and E readings were per the spec I got from Tige support.

BTW, I discovered the bolt pattern issue . . . fortunately without damaging anything.

[bdgregory]

ok, problem identified. While there's continuity from the sender to the gauge, there is a ~200 ohm resistance in the ground wire. I jumped it and the gauge reads correctly. Now I need to either string a new ground wire, or figure out the cause of the resistance.

[UNSTUCK]

thanks for the reply, (I think) your method is what I did. "B+" is the 12V from the ignition. I removed the signal cable at the gauge, not the sender. On this model giving ~12V to the ground terminal on the gauge will read Full. 12V to the signal terminal reads Empty. This is what it did.

You're welcome. I don't understand the idea behind putting 12v to a ground source? The signal wire is the ground wire to the needle motor. The resistance in that ground adjusts the position. It should never have 12v to it.

ok, problem identified. While there's continuity from the sender to the gauge, there is a ~200 ohm resistance in the ground wire. I jumped it and the gauge reads correctly. Now I need to either string a new ground wire, or figure out the cause of the resistance.

This is why it was suggested to check it at the sender. Good work on the find.