This gauge on your Honda Civic lets you know the engine temperature at any given moment. It is an important piece of information you need to have available at all times. Knowing that your car engine is going over its normal operating temperature, will help you prevent serious damage and costly repairs. A malfunction on the gauge is simple to troubleshoot. With this guide, you will be able to locate the fault and make the necessary repairs in a matter of minutes.
Turn the ignition switch to the On position but do not start the engine.
Unplug the wire from the temperature-sending unit. Make sure to keep your hands away from the radiator fan at all times. Then check the temperature gauge to make sure it indicates Cold.
Ground the wire you unplugged using a jump wire with alligator clips, if necessary. You can use the engine block or any bolt on the engine as a ground. Then check the temperature gauge to make sure it reads Hot. If the gauge operates properly as indicated in steps two and three, replace the sending unit.
Disconnect the ground wire at the temperature gauge if the gauge reads higher than cold. If the gauge now reads normal with the wire removed, the wire is grounded. Find the ground and isolate the wire. On the other hand, if the gauge still reads higher then cold when disconnecting the wire, replace the gauge.
Check the temperature gauge fuse if you disconnected the wire at the sending unit (step 2), but the gauge failed to indicate Hot after grounding the wire (step 3). If the fuse is bad, replace it. If the fuse is OK, go on to the next step.
Connect a jumper wire to the ground terminal connection at the temperature gauge. If the gauge now reads Hot, there is an open in the wire between the sending unit and the gauge: Fix or replace the wire. If the temperature gauge still does not respond, go on to the next step.
Check for voltage at the power connection at the temperature gauge. Connect a 12V test light to a good ground on your car and touch the tip of the test light to the power connection at the gauge. It the test light glows, replace the gauge. If the test light does not glow, check the power wire between the gauge and the fuse panel. Fix the connections or replace the wire.
Turn the ignition switch off.