When you car is cold, spin the fan around by hand with a certain amount of force and see how far it spins after you let it go. Do it a few times. Then again when it's hot, try spinning it around with the same amount of force a few times to see how far it spins. When it's hot the fan should spin around significantly less than when cold. If that's true, your problem is probably a finicky thermostat or mucked up radiator, so plan on doing a good radiator flush job soon (look for Ayeroll's excellent and thorough procedure) and replace your thermostat and gasket.

If the spinning of the fan doesn't change much with the temperature of the engine compartment, replace the fan clutch as the other posters suggested.

I suppose it's possible that it's your temp comp board starting to act up, but since this problem seems to be tied to real temperature situations, that's probably not the problem. Still, it's always a good idea to jumper the temp comp board so you can trust the readings on your gage.

if it's cooling off at highway speeds my guess would be the fan clutch...I tossed mine and converted to an elec.

fan from friends wrecking yard $0.00
2 sheetrock screws (yeah I know I'll do it right later) $0.02
adjustable thermostat from jc whitney $13.95 ?
sitting in traffic on a 114 degree balmy west texas afternoon with the temp gauge at 8:00 o'clock ...priceless
Bret
--
rust free in west Texas

i would suggest it's your fan clutch that's not working anymore. When the clutches wear out...they tend to spin around uselessly rather than cool your radiator.

At highway speeds the clutch is useless anyways because of the high volume of air circulating...


This would explain your problem. A brand new one runs about 80 some dollars but a used one from a junke yard woudl run much cheaper. It's an easy do it yourself job as well.

This is the most likely thing i can think of...i would get second opinions as well.


goodluck.

I am assuming that "temperature outside is in the 20's" means 20 degrees Celcius (Centigrad)?

Question; have you tried turning on the heater and running the fan at full blast? If so does it drop the temp considerably? Is the air out of the vents extremely hot?

If yes, turn off the ignition, pop the hood and try to move the fan by hand. If it moves easily, as other have said, your fan clutch is bad. Hope that the clutch and blades are seperate (likely). You can tell because the fan blades are plastic. Cheap part, easy repair.

If no, your quest is more difficult. It could (likely) be the voltage compensation board (if that year had one) or a bad ground for the dash. It also could be a bad temp sensor. If the vents blew hot air, those are the two most likely possibilities.

Onkel Udo

either the rad is clogged and not heating the fan clutch up or the clutch is shot. i'm betting that's it 'cuz a clogged rad would not cool down at speed. good luck, chuck.

Some other things to check. Make sure your gauge actually does work and is not the temp compensation board. Double check the temperature sensor. Check the Fan & Fan Clutch.