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97 Civic overheating

Engine cooling fan will not operate when engine is hot or when A/C is turned on. Condenser fan works fine. Fuses are good and relay’s are good. Fan runs when 12 volts applied directly to fan motor connector. Suspect another sensor is involved, like coolant temperature but don’t know how to check it. Appreciate any other ideas and any help provided. Thanks.

The sensor is on the back side of the block near the coolant outlet, just jumper the sensor to see if the fan runs.

KARC5a gave you some really good advice, but think about it… You say the fan will not turn when the engine is hot or when the A/C is turned on but runs with direct voltage. It has to be the temperature relay or fuse. After you hooked and unhooked the direct voltage can you still be sure that the relay and fuse are good? If it was a case of the engine gets hot when the A/C is on then it would definetly involve the A/C circuitry. I’d start diagnosing from the beginning and isolate the A/C involvement.

Thanks for the suggestions. It turns out it was a bad thermostat (stuck shut) and the fan switch is on the output side of the thermostat and that’s why the fan never turned on. New stat and all is well. Thanks.

You do mean new stat with new fan switch, don’t you?