How to wire an auto temp gauge

Updated February 21, 2017

A temperature gauge can help you monitor the health and efficiency of your vehicle's engine under a variety of operating conditions. Many modern cars and trucks feature a temperature indicator light that illuminates only when the engine overheats. While useful to prevent damage to the engine, an indicator light does not provide you with information about the actual temperature or the rate of rise of the temperature. Once installed, aftermarket temperature gauges are easily wired using common hand tools.

Use an adjustable wrench to disconnect the negative battery terminal.

Choose a location on the vehicle's firewall that can be drilled safely to provide a path to run the gauge wiring through. Use a drill with a 1-inch bit to drill a hole through the firewall in the chosen location. Insert the included grommet into the 1-inch hole.

Run the wiring harness from the temperature gauge through the 1-inch hole in the firewall to the vehicle's temperature sender. Plug the harness connector into the temperature sender. Plug the other end of the harness connector into the back of the temperature gauge.

Connect the white wire from the temperature gauge to a wire from the vehicle's dash lighting using a tap splice. Strip 1/2 inch of insulation from the end of the black wire connected to the temperature gauge. Locate a screw connected to a metal part of the vehicle near the temperature gauge. Loosen the screw by turning it counterclockwise with a screwdriver. Wrap the stripped end of the black wire around the screw head and then tighten the screw.

Strip 1/2 inch of insulation from the end of the red wire connected to the back of the temperature gauge. Slide the bare end of the red wire into a butt splice. Slide one end of the cartridge fuse into the other end of the butt splice. Crimp the butt splice securely. Connect the other end of the cartridge fuse to a switched 12-volt wire that is powered when the vehicle's ignition is in the On or Acc position.

Connect the negative battery terminal and tighten it securely. Test the operation of the temperature gauge. Check the connections and fuses if the gauge does not operate properly.


A service manual or wiring diagram will make it easier to identify the proper wires to connect to.


Consult a dealer or service manual before disconnecting the factory temperature gauge wiring.

Things You'll Need

  • Adjustable wrench
  • Drill
  • 1-inch drill bit
  • Wire strippers
  • Tap-splice connectors
  • Butt splices
  • Crimpers
  • 1-amp cartridge fuse
  • Phillips screwdriver
  • Flat screwdriver
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About the Author

David Young has written for the website for the Save Darfur Coalition and is currently writing articles for various other websites. Young holds a Bachelor of Arts in philosophy from Western Carolina University.