QuestionQUESTION: i own a 1970 dodge charger, and can't get any power to my gauges, there is a blue wire that goes to the fuel sending unit, if i ground this wire out the gauge will move, i have changed the sending unit three times, also no power to the oil preassure gauge or temp gauge, i hate driving the car without these gauges, i have aftermarket gauges hooked up but no fuel gauge.
ANSWER: Grounding the wire that goes back to the sending unit in the tank should peg the gauge in the dash, if it doesn't, you probably have a bad gauge regulator. If so, this would also affect the other electrical gauges except the ammeter, if your car has one.
The gauge regulator is still available - if you go to a NAPA store and ask for an "Instrument Regulator" they will have one.
You can check your regulator by putting a meter or a test light on the wire that goes from the fuel gauge back to the tank sender - you should see a blinking light on your test light, or your meter should move from 0 to 12 volts every second or so. If that happens, your gauge regulator is OK.
Your fuel tank sender has to be grounded to work - it depends on the mounting bolts that hold the tank in place to provide the ground, but maybe you have some dirt or something else that is causing the tank to make poor contact to the chassis. You can add a wire to one of the sender mounting screws and run that wire to a known good ground - like a bumper bolt - and that should clear up that problem for you.
As far as the aftermarket gauges, you're on your own.
The original gauges will work if the regulator is OK and the wires are all connected correctly - there is only one wire to each sender from the dash gauge unit. If they are not connecting, your problem is probably in the bulkhead connector - especially if the car has lived in the east - they are famous for getting corrosion and oxides on the bulkhead connections. Just take them all apart and clean them so you have bright shiny metal on both ends of each wire. This is a big job (there are 40 pins in those connectors), but it will solve a lot of electrical problems for you.
Dick
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QUESTION: i checked the power wire with a test light going to the tank, the light was palsating wich would indicate that the dash limiter was working, i am running a electric fuel pump, i know on these old mopard there os a grounding strap that onectes from the sending unit to the fuel line to groung the sending unit to the frame, i ran a wire from the negetive side of the battery to the sending unit and got nothing on the gauge, i'm beginning to think i bought junk sending units from ebay, even though they are suppose to be new doesn't meen they are not junk, i priced one at napa wich i may go ahead and buy, they are supplied by the original supplier that made them for chrysler. thanks doug
AnswerOK, I think that is a wise move. If the sending wire is pulsating, you have a good gauge regulator, as you say, so the next step is to try a sender that you know is good. You can test it out of the tank first, but just hooking it up and grounding the mounting flange to the bumper. Move the arm and the gauge should respond slowly (be patient, it takes a few seconds to respond after you move the arm) - but it should work.
You can also test the senders with an Ohmmeter - if you have access to one, you can verify that the ohms reading changes from very low: about 10 ohms or even less for a full tank (arm all the way up, of course) to about 70 ohms or so for an empty tank.
Dick
