Midlife,not getting power to gauges/cluster pins

[3pedal 95]

Fuel gauge/gauges not moving...gauge lights working...new tank sending unit...70 mustang

[Midlife 814]

Lights have nothing to do with the gauges working: they are two separate systems.  As for your problem: first briefly ground the sending unit wire for the fuel to ground and see if the gauge pegs with the key in ACC.  If it does, then the wiring is good and the sending unit is bad or not grounded.  If it doesn't, I'd first check the constant voltage regulator on the back of the dash cluster.

Finally, the damn flexible circuit card may have given up the ghost...

[3pedal 95]

Thanks...Ok...I removed the dash gauge assembly...how do you test the regulator

[Midlife 814]

By replacing it...nearly impossible to test with the circuit card in place.

[3pedal 95]

I replaced it with a new one...no difference so I reinstalled the old one...hmmmm...I'll keep playin

[Midlife 814]

Did you ground the sending unit wire and did the gauge peg?

[danno 128]

A common failure is the flexible circuit card.  With the panel removed, you can check for shorts between the flexible card and chassis.  If you have an ohmmeter, check the resistance between  the metal frame (where it gets screwed into the chassis at the speedometer,) and  either contact of the fuel gauge.  You need to unplug the constant voltage unit to do this test.   It better be more than  1000 ohms ( 1 kilohm).  If it is less than 100 ohms, that means you have a short between the constant voltage output and chassis ground. 

[bigmal 225]

I had problems with my gauges but it was with temp, oil and fuel not working. It turned out to be the post (bolt) having shorted on the case of the instument panel. In my case it stopped all three gauges working. As the cardboard insulator covers the opening to the gauge I could not see that it was touching the panel. As I have changed to Midlife's wiring harness to replace the circuit board it was easy to troubleshoot. With the wires disconnected I checked for continuity between the post and the frame. (With Midlife's help).

If you only have a problem with fuel then this probaby wont pply to your situation.