Fuel gauge mystery

rotorwrench said:
The ground polarity is important to a switching voltage regulator and that's why they have a ground wire on the Runtz. Make sure that the screw stud terminal on the runtz does not make contact with any of the surfaces of the gauge that can ground the 12-volt input. Make sure that each runtz unit has its own power wire coming from the power source wire. They can not be connected in series with other units, only in parallel with the original power wire unless they already were connected each to their own power wire.

If all the wiring is correct then there is likely a problem with the way the runtz was made, ie one of the connectors to the little voltage reducer was miss-connected for proper operation. These things only work with negative ground 12-volt systems but it sounds like that's the way the vehicle already is set up.
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My power wire is jumped from one runtz to the other. I finally have a chance to go down to the shop and do further tests. I will run a new lead to each runtz and see what happens. Thanks all.
 
Mystery solved! Thank you one and all. I tried running a single power wire to the fuel gauge runtz, no difference. Next I switched the sender wire and the power wire on the fuel gauge. No difference. Then I swapped the runtz unit with the one from the temp gauge and wired them both up. Now my temp gauge sends the needle in the wrong direction when the panel is grounded. I will call the guy at 5th st garage in the morning and also re-wire the gauges so each one has it's own power supply. Can I take the power wire from the ignition switch and mount it to a stud on a piece of bakelite and then run the 3 wires from that stud to each gauge?
 
That should work since it would be the same as running separate wires from the buss. The instructions on the web site just say not to connect power to one and then jumper from there to another since both runzes would be affected when in series with each other. If you call Randy Rundle, ask his advice on the matter.
 
I will do that. I like how there are experts in the field of old fords, like Randy that run businesses and post up their phone # and will actually talk to us. Mac VanPelt is also one of those. Back in the early 90s I had a question about my 38 tonner and so I called directory assistance in Detroit and got James Wagner ( Ford trucks since 1905) on the phone. We talked for a half hour and had some laughs and he answered all my questions happily. Jere Jobe and Bob Selzam also come to mind as old phone pals. Now we have forums and I love this venue also.
 
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