Typical fuel and temp gauge issues

[Mark1972]

Hey all. The only two gauges not working on my 1970 Plymouth Satellite. My wiring was torn up a bit when I got the car, so I'm following the wiring diagram I bought, but stuck now. I'm getting no power at all on the dark blue wire from the dash to the body plug, and then to the fuel sending unit. I've installed a new RTE limiter, which is working properly(that us to say its blinking like I think it's supposed to when the key is on). Now the next part seems like a dumb question, but my fuse panel is missing the far left fuse. It reads as a 20amp fuse for accessories. But it wasn't there when I got the car. The top clamp that would hold the fuse is missing along with whatever wire would go into and out of it. So would that explain the fuel and temp gauge not working? Or are those two things related at all? Everything else works on the dash. All lights work. I've replaced all the other fuses. I've read a bunch of posts on fuel and temp gauges not working but none seem to have the issue of no voltage. So I'm here for help. Again.

 

[FrnkNsteen]

I'm getting no power at all on the dark blue wire from the dash to the body plug, and then to the fuel sending unit.

First, let me say that I don't have much experience with the non rally gauges or wiring, but I don't believe you should have power to the fuel sending unit. Power should go to one side of your gauge and the other side of the gauge will go to the sender. The wire that goes from the gauge to the sender is actually your ground, and the resistance in that line is what operates your gauge, as resistance changes with fuel level.

A quick test would be to ground that wire to chassis ground and see if your gauge reacts. If your gauge climbs when you ground out the sender wire, then your gauge is working and you have an issue with your sending unit. That could mean that the sending unit is bad, or it could be a bad float on the sender arm.

First thing I would do is check for power to one side of the gauge, then, if you have power to one side of the gauge, next ground out the wire that goes from the gauge to the to the sender and watch for a reaction on the gauge. Same goes for you temp gauge. If those wires cause an action on the gauge, focus on the sending units. If not,.. the gauge itself could be bad. A bad limiter that gives full 12volts to the gauge can kill the gauge.

 

[beanhead]

If I'm remembering, and I don't have a '70 but those gauges get their power from the circuit board, not directly from a separate fuse...is there a working ashtray light/lighter, radio, tach etc in your car? Those would be 'accessories' fed straight off the fuse block. FrankNsteen is right on with the testing procedure. When you do this only turn the key on long enough to see if the gauge moves (it should jump right away if it's working) then immediately turn the key off or you can damage the limiter. If you see the gauge needle rise this will confirm at least the gauge and it's sending wire are good. If nothing happens obviously you'll have to do some more tracing but I would definitely check the big round plug on the back of the instrument panel, there is a pin soldered to the end of each wire and sometimes, when the plug is pushed in, some of the pins push back out of the plug instead of going into their homes. Good hunting!

 

[Mark1972]

Hey guys. Thanks for the help. It appears as if my gauges are both smoked. I had a faulty voltage limiter and am now worried that new gauges may be needed. I've got 1 more thing to try tonight and if still nothing then I'll be shopping. Anyway, as always, I appreciate the advice.