fuel gauge wiring

[46ford]

I've been running no fuel gauge for awhile. Just got the new float from Mac's so I'm going to put the sender back in and hook it up. Sender is nice, looks to be in good shape with very little corrosion anywhere.

Does one wire from the sender go to ground and one to the gauge in the dash? I assume the other gauge connection goes to the battery terminal on the gauge block same as the other gauges. Is there any risk of fire from running current through the sender? (I remember the movie "class action).

 

[Old Henry]

I've been running no fuel gauge for awhile. Just got the new float from Mac's so I'm going to put the sender back in and hook it up. Sender is nice, looks to be in good shape with very little corrosion anywhere.

Does one wire from the sender go to ground and one to the gauge in the dash? I assume the other gauge connection goes to the battery terminal on the gauge block same as the other gauges. Is there any risk of fire from running current through the sender? (I remember the movie "class action).

You have it right. Current runs from ignition switch, through gauge, to sender, through sender to ground. No sparks nor heat created in sender so no risk of detonation.

 

[Ken Bull]

I have a ?. My Guage doesnt work unless I attach my test light to grnd & touch the probe to the hot wire at the guage & it works fine??? Is test light acting like a resister? Whats up?? Thanks Ken

 

[Old Henry]

I have a ?. My Guage doesnt work unless I attach my test light to grnd & touch the probe to the hot wire at the guage & it works fine??? Is test light acting like a resister? Whats up?? Thanks Ken

Gauges made for 6 volt will only work on 6 volts. If you're trying to get an original 6 volt gauge to work on 12 volt you will need a voltage reducer. It is much more complicated than just running the current through a resistor although the test light may act as one as you have discovered. Here is what you'd need: http://macsautoparts.com/early-v8-f...h-gauges-v12871/camid/F30/cp/340RW35U1000017/

 

[46ford]

You have it right. Current runs from ignition switch, through gauge, to sender, through sender to ground. No sparks nor heat created in sender so no risk of detonation.

So without that gauge in the circuit (or if a loose positive wire ever got in contact with the wire going to the sender...ka boom???

 

[Old Henry]

So without that gauge in the circuit (or if a loose positive wire ever got in contact with the wire going to the sender...ka boom???

Try it and see. Hook the lead of the sender to one battery post and ground the body of the sender to the other post and see what happens. I haven't tried it. Doubt if anyone ever has. Doubt the sender will even heat up because the rheaostat of the sender is made of resistor wire. Let us know what happens.

 

[46ford]

Try it and see. Hook the lead of the sender to one battery post and ground the body of the sender to the other post and see what happens. I haven't tried it. Doubt if anyone ever has. Doubt the sender will even heat up because the rheaostat of the sender is made of resistor wire. Let us know what happens.

Well if I thought that was true I wouldn't be asking, I would just install it.

The rheostat is not visible in my sender. There is just a flexible diaphragm that moves with the lever. I know a lot of the resistance in the system is in the gauge, too. Frankly don't know much about the system but the thought of inadvertently getting 6V to the wrong terminal of the gage makes me want to leave the thing alone.

Doubt anyone has?

 

[Ken Bull]

My electrical system is stock 6V positive grnd. thats why I ? My brain says if the test light lit bulb makes the guage work then I must need to install a resister between ingnition switch & guage. What Ohm value do I need?? Thanks for imput--Ken

 

[Juergen]

Ken, There is something else going on here that doesn't make much sense. If your test light would make the gauge work, then turning on your dash light, or your dome light would do the same thing. The test light is hardly causing any load to the voltage applied to the gauge.

Check to see if probing with the test light is causing a bad connection to become good at the gauge. Don't ground the test light as you probe with the other end and see if you get the gauge to work. That would indicate a bad connection at the sending unit.

 

[19Fordy]

46Ford, I am not an electrical expert but I have attached a photo of the dash guage wiring of the tank sending unit in my 40 Ford. I think it's the same as your 46. In my system one wire goes from the center top screw on the sending unit to the dash gas guage. Another wire then goes from the other terminal of the gas guage to the ignition switch. The gas tank sending unit grounds itself to the gas tank with the screws that attach the sending unit to the metal tank and the tank is grounded to the frame of the car. To be sure the gas tank sending unit is really grounded, I ran a separate wire from one of the screws holding the sending unit to the frame. I interpreted your first post as saying that you had two wires coming off your sending unit. That is not so in the stock 1940 ford and I doubt that it is true of the 46 Ford. The other photos are of a 1951 Mercury tank sending unit/guage hook up. It works on the same principle as the older Fords. i hope this helps.

 

[Tinker]

46ford, I've read a couple of your threads here asking questions. So I have a question for you.

Did you do the 12volt conversion? Was everything done to work with the 12volt system when it was converted, bulbs, gauge resistors, generator/alt?

 

[Tinker]

My electrical system is stock 6V positive grnd. thats why I ? My brain says if the test light lit bulb makes the guage work then I must need to install a resister between ingnition switch & guage. What Ohm value do I need?? Thanks for imput--Ken

Doesn't the tank need to be grounded for the gauge to work? Maybe why the gauge only works when you complete the circuit with the test light. Tank bolts to frame, frame is grounded. Paint maybe interfering with your ground contact.

Ken, found this thread for you. See post #6.
http://fordbarn.com/forum/showthread.php?t=53036&highlight=fuel+tank+ground

 

[Ken Bull]

Thanks I will recheck my grnds.

 

[Henry/Kokomo]

Sure sounds like a grounding issue to me. Your test lite was grounding the sender and making the circuit, albeit with extra resistance (the bulb).

 

[46ford]

46ford, I've read a couple of your threads here asking questions. So I have a question for you.

Did you do the 12volt conversion? Was everything done to work with the 12volt system when it was converted, bulbs, gauge resistors, generator/alt?

No, I kept mine all 6 volt. I've never converted a 6V car to 12V, always kept them stock, and I've owned a half-dozen or so.

 

[TJ]

Run an extra ground wire from one of the sending unit mounting screws to the frame. Many times the gas tank does not get a good ground. The test light is completing the ground circuit.

 

[Tinker]

Ooops 46ford, excuse me for my mistake. It was another person with a very similar name that just joined and I confused that person for you. Sorry and ignore...