(Other systems may use a different procedure.)

There are four major sources of temp gauge problems. Read on for the testing procedure.

1. The temp gauge in the engine control panel may be defective


  • Disconnect BROWN sender wire from “S” terminal on gauge
  • Turn on ignition switch
  • Pointer must deflect to extreme left
  • By temporarily shorting together the “S” (sender) and the “G” (ground) studs, pointer must deflect to the extreme right
  • Re-connect the BROWN sender wire to the gauge after the test

2. The brown sender wire may be disconnected from the sending unit at the engine or shorted to ground


  • Disconnect brown sender wire from terminal at sending unit on engine
  • Attach brown wire to a known ground, such as engine block or battery negative
  • Do not assume the body of sender is grounded
  • Turn on ignition switch
  • Pointer must deflect to extreme right, as in previous test. Disconnect brown wire from ground.
  • If pointer still deflects to extreme right, brown wire is grounded at some point between the sender and gauge.
  • Check all connection points on brown wire or replace the entire wire

3. The sending unit may not be properly grounded to the engine block


  • If the gauge tests “Good” and brown wire tests “GOOD”, touch brown wire to the body of the sender (the flat area where you would place the wrench to install the sender.)
  • Make sure this area is free of paint. If pointer does not deflect to right, as in test above, the sender body is not grounded.
  • Remove the sender and inspect the threads. If necessary, remove an Teflon tape or Pipe Dope compound.
  • Clean the threads, apply some coolant to the threads, and reinstall the sender in the engine

4. The sending unit in the engine may be defective or the wrong unit may have been installed


  • If steps 1, 2, and 3 do not uncover the issue, the sending unit in the engine is defective, or
  • it is possible the wrong unit may have been installed. The correct sending unit has a specification of: Stewart Warner, 240 to 33 OHMS resistance

There are several other resistance specifications available, but those sending units will not work in this application.

Test Procedure, W/ Temp Gauge Panel Department, April 22, 2003

Whittier, CA, 90601  Seaward Products

Jamie Pett, Bella Luna, #614