Author Topic: Testing for a inoperative fuel gauge sending unit  (Read 15298 times)


  • Senior Member
  • ****
  • Posts: 1542
Testing for a inoperative fuel gauge sending unit
« on: April 20, 2010, 10:29:59 PM »
I recently came up with a simple way to test the sending unit without removing it or the tank.
 The resistor portion of a spare headlamp switch can be attached with alligator clips between the wire for the sending unit & the ground wire. When the knob is turned (which would originally dim the dash lights) the gas gauge will move from E-F & vice versa if the sending unit is bad, but the rest of the system is all working correctly. If the gauge doesn't move, additional investigation of the wiring &/or the gauge is in order.
 I had an inoperative fuel gauge & wasn't sure if I should start under the vehicle or in the dashboard. This took about 15 minutes to rig up & saved a whole lot of time (the gauge was able to be controlled by the dimmer switch) since I didn't start at the dashboard  ;)
Hope this helps someone someday, Lorne

Offline VileZambonie

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 19073
Re: Testing for a inoperative fuel gauge sending unit
« Reply #1 on: April 21, 2010, 07:51:14 PM »
Most factory units are 0-90Ω so any good variable resistor in that range will do the trick, just make sure the other terminal on your potentiometer is connected to a good clean ground.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10