Smiths Fuel Gage Troubleshooting

For other electrical troubleshooting see our Wiring Primer.

This page  covers only the later (~Chassis 200-up) Smith gages from Nisonger or Caerbont

Note: Some of the wiring instructions for later cars didn't show the ground wire on the center terminal.
Gage diagram

OVERVIEW:

Almost all Nisonger gages use a Stewart-Warner mechanical sender.  The early Caerbont gages were supplied with an electronic sender (from Centroid Products - See directly below) with two or three-wire connections.  A volt-ohmmeter with a 1K ohm range is very helpful with the Centroid sender.  Later Caerbont gages functioned well with the S/W sender.

The Smith gages require a signal from the sender as shown below:

Nisonger

 Tank empty - 240 ohms
Tank full - 25 ohms

Caerbont

 Tank empty - 400 ohms
Tank full - 50 ohms

Sender wiring

Centroid Sender Connections

Some senders do NOT require a power connection to the pink wire in the harness.

SYMPTOM

Gage doesn't read at all:

If there is only one wire (white) from the tank sender:  

  1. Are the wipers and tachometer also dead?  If so, check the 3rd fuse down on the passenger's side fuse box.  Replace if necessary.
  2. Disconnect.the wires at the left front of the fuel tank.
  3. Turn the ignition switch on.  Ground the white wire of #62.  If the gage doesn't go to full, check the dash-to-rear multi-pin connector at the driver's footbox.
  4. With the ignition on, check that you have some voltage at the white wire (#62) of the harness.   This is the signal from the gage, so its value may vary with the VOM brand, but it should be more than 6V.  If the wire is dead, check the multi-pin connection between the dash and rear harness at the driver's footbox.  If the voltage is zero, the connection at the gage or the gage itselft may be bad.
  5. If the gage goes to full, the sender may be bad.  Use a VOM to measure the resistance between the white tank wire and ground.  The fuel tank itself can act as a ground. If the value you measure doesn't fall within 240 ohms (full) and 25 ohms (empty), the sender is probably bad.  If either value is infinite or zero, the sender or the connections to it are defective.

If there are two wires coming from the tank sender:

  1. Are the wipers and tachometer also dead?  If so, check the 3rd fuse down on the passenger's side fuse box.  Replace if necessary.
  2. Disconnect.the wires at the left front of the fuel tank.
  3. With the ignition on, check that you have 12V at the pink wire (#62) of the harness.  If the wire is dead, check the multi-pin connection between the dash and rear harness at the driver's footbox.
  4. With the ignition on, check that you have some voltage at the white wire (#62) of the harness.   This is the signal from the gage, so its value may vary with the VOM brand, but it should be more than 6V.  If the wire is dead, check the multi-pin connection between the dash and rear harness at the driver's footbox.  If the voltage is zero, the connection at the gage or the gage itself may be bad.
  5. With the VOM, check the resistance between each of the wires from the sender and ground:
    White wire to ground: 400-500 ohms
    Pink wire to ground: 520-1000 ohms
    If the values are reversed, the connections to the sender may be incorrect.  Use jumpers to connect the white wire from sender to the pink #61 wire and vice versa.    If either value is infinite or zero, the sender or the connections to it are defective.

Gage reads incorrectly but responds when the ignition is turned on.

If there is only one wire (white) from the tank sender:  

  1. Disconnect.the wires at the left front of the fuel tank.
  2. Turn the ignition switch on.  Ground the white wire of #62.  If the gage doesn't go to full, check the dash-to-rear multi-pin connector at the driver's footbox.
  3. With the ignition on, check that you have some voltage at the white wire (#62) of the harness.   This is the signal from the gage, so its value may vary with the VOM brand, but it should be more than 6V.  If the wire is dead, check the multi-pin connection between the dash and rear harness at the driver's footbox.  If the voltage is zero, the connection at the gage or the gage itself may be bad.
  4. If the gage goes to full, the sender may be bad.  Use a VOM to measure the resistance between the white tank wire and ground.  The fuel tank itself can act as a ground. If the value you measure doesn't fall within 240 ohms (full) and 25 ohms (empty), the sender is probably bad.  If either value is infinite or zero, the sender or the connections to it are defective.

If there are two wires coming from the tank sender:

  1. Disconnect.the wires at the left front of the fuel tank.
  2. With the ignition on, check that you have 12V at the pink wire (#62) of the harness.  If the wire is dead, check the multi-pin connection between the dash and rear harness at the driver's footbox.
  3. With the ignition on, check that you have some voltage at the white wire (#62) of the harness.   This is the signal from the gage, so its value may vary with the VOM brand, but it should be more than 6V.  If the wire is dead, check the multi-pin connection between the dash and rear harness at the driver's footbox.  If the voltage is zero, the connection at the gage or the gage itself may be bad.
  4. With the VOM, check the resistance between each of the wires from the sender and ground:
    White wire to ground: 400-500 ohms
    Pink wire to ground: 520-1000 ohms
    If the values are reversed, the connections to the sender may be incorrect.  Use jumpers to connect the white wire from sender to the pink #61 wire and vice versa.
  5. If the gage goes to full, the sender may be bad.  Use a VOM to measure the resistance between the white tank wire and ground.  The fuel tank itself can act as a ground. If the value you measure doesn't fall within 240 ohms (full) and 25 ohms (empty), the sender is probably bad.  If either value is infinite or zero, the sender or the connections to it are defective.