Register now to get rid of these ads!

Hot Rods Noob fuel gauge question

Discussion in 'The Hokey Ass Message Board' started by Jasper6120, Feb 19, 2017.

  1. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    Hey everyone

    I'm trying to get the fuel gauge up and working on my 53 Chevy, but I'm having no luck and I'm starting to doubt that I'm reading the wiring diagram properly.

    The bit that is causing the confusion is the "wire" running beneath the two points on the gauge itself. I assume that this is just representation of the gauge being bolted/grounded to the chassis? Other than that there's only a wire coming off the ignition switch and one going to the sender (as well as a voltage reducing diode over the hot side).

    When the sender side is grounded the dial moves from already reading empty to about 1mm closer to empty. Not as yet has the dial ever moved towards full. Nothing is making sense to my small bird brain. Anyone have hints on what the problem could be?

    Cheers

    J
     

    Attached Files:

  2. This is the same diagram that is in my 55 service manual. It appears to show the power side only. The manual talks about having a common connection from the gas sender to two coils (1 guage and 1 limiting coil). Looks odd to me to, however, I guess if you have a complete factory setup it should work.
     
    Jasper6120 likes this.
  3. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    This car has been rewired from scratch so I don't have a factory harness for reference. It's all a bit ambiguous really.


    Sent from my iPhone using The H.A.M.B. mobile app
     
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 47,403

    squirrel
    Member

    that is a lousy drawing! That wire is internal to the gauge, and connects one side of one of the internal gauge magnets to the other internal gauge magnet..

    You want to connect the ignition wire to the I terminal on the gauge, and connect the sender wire to the S terminal on the gauge. Make sure the gauge housing is grounded (no rust, etc on the gauge housing, or where the housing contacts the dashboard). Make sure the sending unit is grounded (they usually had a separate ground wire for this, connecting from a screw on the floor pan, to one of the sender retaining screws).

    When the sender wire is shorted to ground, the gauge should show Empty. When the sender wire is disconnected, it should read Full. If this is not the case, then your problem is with the gauge itself, or the ground or power connections to the gauge.
     

  5. It says when the tank is empty the sender cuts off the resistance in the sender and it is the limiting coil that shows the tank as empty. So with the sender / tank not grounded the guage will always show empty. Try placing the sender in the 1/2 position and appropriatly ground the guage set and the sender / tank. None of the connections shown on your diagram should be grounded.
     
    Jasper6120 likes this.
  6. My first step would be to use a multimeter on ohms and measure the resistance from empty to full and work forward from there. Web shows 0 empty and 30 ohms full. However, for a "limiting" coil to work, I assume the fuel sender will disconnect itself before reaching 0, otherwise it won't limit.
     
    Jasper6120 likes this.
  7. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    I will pull the gauge out tomorrow and give it a proper look, as well as the sender, which I anticipate will have some issues since it had been sitting for a good 30 years.


    Sent from my iPhone using The H.A.M.B. mobile app
     
  8. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,406

    Rusty O'Toole
    Member

    I think the gauge should read Full when you ground the sender wire and Empty when you disconnect it.
     
    Jasper6120 likes this.
  9. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    Thanks for that info squirrel. That really does clear up a lot of things and yes, that diagram (from the manual I might add) is pretty ordinary.
    Rusty that's what I've heard about fuel gauges too, unless somehow these 50's GM ones are different?


    Sent from my iPhone using The H.A.M.B. mobile app
     
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 47,403

    squirrel
    Member

    Zero ohms (sender wire shorted to ground) is empty, 30 ohms (or wire disconnected) is full.

    On a Ford, yeah. This is a Chevy. They're backwards.
     
    koolkemp and mad mikey like this.
  11. Just to add some info. The fuel gage is just an ohm meter, measuring resistance, that is calibrated as 0-30 ohms being represented on the gage as Empty-Full. The sender in the tank is a variable resistor. The gage itself needs 6V power, and the sender wire has no power on it. Since it measures resistance, cleanliness of the grounds is important for accurate readings.
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 47,403

    squirrel
    Member

    ....and it will probably work on 12v, but it will be a bit aggressive, and might burn out soon! A 6v solid state voltage regulator is a good idea.
     
  13. MidwestOldie
    Joined: Jul 7, 2016
    Posts: 59

    MidwestOldie

    Pull the sender & gauge, bench test it with new wires and 6V. Good ground on the sender. Moving the float should make the needle move.
    If in the car, run a new test wire from the gauge to the sender, and check fuel. That single wire on mine was defective. If the sender has proper resistance, perhaps the gauge. Not everyone has a spare gauge to test. Those few pieces can be annoying.
     
    koolkemp likes this.
  14. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    I pulled out the gauge this morning. It turns out that the super fine wire going to the hot side coil has been fried. Just dangling there like a busted light globe. I checked to see if I'd anything wrong. The voltage reducing diode comes up as 7.2 volts on the voltmeter so a little hotter than stock but I can't imagine that would be enough to fry it. I've never seen the gauge in action so it could have busted many years ago. Now for another noob mission to solder the wire back together and see if the gauge comes to life

    [​IMG]
     
  15. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    After soldering the wire back on I wired the car from the diode to ground and hey presto, the gauge shot up to full. Then ran straight off the sender and it went up to just above empty, which sounded about right. Things were going well but then when checking the gauge to ground again it only moved up a few mm. It doesn't go to full any more. I'm thinking either the soldering wasn't good or gauge has had it. I also noticed a fair amount of warmth coming from the back of the power terminal on the back of the gauge. Is this normal?


    [​IMG]

    [​IMG]

    [​IMG]
     
  16. squirrel
    Joined: Sep 23, 2004
    Posts: 47,403

    squirrel
    Member

    those things are tricky....are you sure you have the wire going to the correct place? and are the I and S terminals clearly marked, so you're not connecting them backwards?

    7.2v should be fine for the voltage, that's what a 6v battery gets when it's being charged.
     
    Jasper6120 likes this.
  17. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,129

    d2_willys
    Member
    from Kansas

    When repairing the gauge, taking one turn off the coil won't bother the readings much.
     
    Jasper6120 and squirrel like this.
  18. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    Now that's an idea! I'll do that today and report my findings


    Sent from my iPhone using The H.A.M.B. mobile app
     
  19. 53 ford
    Joined: Apr 8, 2012
    Posts: 143

    53 ford
    Member

    53 Ford trucks are 6 volt. On the back of the gauge panel is a constant voltage regulator, it reduces the gauge voltage to 3 volts. If the battery voltage gets low the gauges will still be accurate. I don't know if chevys work the same but they may. To check a ford gauge wire a d cell flashlight battery across the gauge terminals, one and a half volts should read one half tank. Two d cells, three volts, should read full. Good luck, Harley
     
  20. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    I'm having no luck! I bought three voltage reducing diodes to be safe and all three of them seem to be fried. They started off feeding through about 8 volts, then they get quite hot and go up to feeding 14 volts :( I must have linked them up to the wrong tab on the ignition switch and pumped through too many amps maybe? This is all new to me this stuff


    Sent from my iPhone using The H.A.M.B. mobile app
     
  21. squirrel
    Joined: Sep 23, 2004
    Posts: 47,403

    squirrel
    Member

    what kind of thing are you buying? part number?

    I'd use an LM7806 voltage regulator, but I'm a wannabe electronics geek.


    btw the Ford gauges work completely differently than Chevy gauges, so suggestions about them, don't apply.
     
  22. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    I am using a Runtz Diode voltage reducer. I just noticed on the sale page that it 'will handle up to 0.4amps'. The dash gauges are using 1amp current
     
    Last edited: Feb 22, 2017
  23. squirrel
    Joined: Sep 23, 2004
    Posts: 47,403

    squirrel
    Member

    do you have a failed one, that you can cut open the shrink tubing, and take a picture of what's inside? or is it just a diode?
     
  24. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    It's just a diode. Pure and simple. And yes, the problem I encountered was due to the amps going into the dash being too high for it. When I ran a multimeter on the circuit it measured a current of 1 amp, but the diode is only good up to .4amps. I don't really know what I'm talking about though.

    [​IMG]
     
  25. squirrel
    Joined: Sep 23, 2004
    Posts: 47,403

    squirrel
    Member

    uh....amps are "drawn", they are not "put into".

    Volts are "put into".

    I still suggest you get a LM7806 voltage regulator.

    But I also think the gauge should work on 12v, but it might fry the coils after a little while.
     
  26. Jasper6120
    Joined: Jul 18, 2007
    Posts: 470

    Jasper6120
    Member
    from Australia

    Brain officially broken. I purchased one of them Runtz voltage reducers, bought a new (second hand) 53 Chevy fuel gauge, wired it up exactly per instructions, and I'm getting the same problems as before. Firstly - I'm getting a reading of 10 volts after the voltage reducer, and secondly, when I run the new gauge to ground it still only raises the dial up to just above empty. I must be doing something wrong but I have no idea. Maybe wired to the wrong ignition switch terminal? Wrong wire resistance? (Just standard 5 amp auto wire though..)


    Okay, I fixed it. I had a temporary earth wire running to the gauge housing, however the earth lead was stuffed. So the voltage reducer didn't work and the gauge didn't have the flow to earth to make the gauge read full.
     
    Last edited: Mar 9, 2017

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2020 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.