I have a 1995 jeep cherokee 4.oL in which the auxillary fan only comes on when I turn the control panel to defrost. I can cruise along and watch the temp rise to about 212 on the gauge then I turn on the defroster which turns on the electric fan and the engine cools down almost immeadiately. I checked the relay and notice the same exact relay was used for the AC so I switche the two to see if the auxillary fan might come on before the car heats up to over 210. Any ideas? I would really appreciate it.

Two things: The A/C gets excercised with request for defrost but shouldn't cool the engine down but explains the fan coming on. It would use the same relay.

The engine has a thermostat to allow it to heat up to temp no matter how much air is fanning the radiator. Sounds like the thermost doesn't close all the way for warm up.

If aux fan is aftermarket it could have been wired to come on with compressor on only not just when A/C is asked for as compressor will shut down when it's too cold anyway,

T
Tom Greenleaf - MetroWest Boston - USA
http://www.acsource.com/

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http://www.autoacsystems.com/tomgreenleaf/