Questions and Answers

Honda Civic Temperature Fluctuates Q. Just wanted to say thanks for all the helpful hints you give. I have a 1994 Honda Civic LX, 1.5 liter 4 cylinder and automatic transmission. Odometer reads 155,000. Lately the temperature gauge is fluctuating a lot. I noticed it when I am on the highway. When there is heavy traffic and I am not moving much it gets hot.

When traffic loosens and I go it cools off. I don't have a leak and I changed my water pump in December 2003. Any ideas you can give would be greatly appreciated. I was thinking it was the thermostat, But you would know better.

Thanks,
Carlos

A. This is a classic symptom of an inoperative electric cooling fan. When you are moving, air comes in and flows through the radiator, cooling it down. When you are stopped, no air flows through the radiator and thus no cooling takes place.

To confirm this start up the car and let it idle with a thermometer in the radiator. The fan should come on between 190° to 200°F. It should shut off at 182° to 188°F.

If it doesn't, you probably have a bad Cooling Fan Motor Switch or relay. It may be possible the fan motor itself is bad. If you run a fused, 15 amp, jumper wire to the blue wire of the fan motor connector, the fan should run. if it doesn't leave the wire hooked up and ground the black/wire.

Left Front Of Engine Compartment.

If the fan motor comes on, the ground wire is bad. If the fan motor doesn't come on, the fan motor is bad.

If the fan motor comes on, you need to check the Cooling Fan Motor Switch. Check for power at the green wire of the Cooling Fan Motor Switch connector. If there is no power there you have either a bad Cooling Fan Motor Switch Relay, an open between the Cooling Fan Motor Switch, Cooling Fan Motor Switch Relay or the fuse, or a blown fuse. I assume this was the first thing you checked.

Right Side Of Engine.

Here is a wiring diagram to help you track down the problem.

It is a fairly simple circuit and you should have little trouble finding the problem.