OK, I've read all the posts on the cooling fan but still not sure if it is the relay or the fan clutch that is failing.
Symptoms: Fan runs from start up to shut down. Always turning at full speed whenever the engine is running. While driving in the mountains in snow country, I can barely get the engine to get warm enough to turn on the heater.
When engine is stone cold, I can turn the fan by hand but it is not free spinning. I can try and spin it but it will only spin maybe 1/4 turn with a hard push on my part.
Does this sound like the fan clutch is bad?
Oh, yeah, I forgot. 1996 Grand Cherokee with the 4.0 six engine.
The engine should still warm up with the fan locked up. It does sound like your fan clutch has failed, but the not warming up is likely a failed thermostat. The 4.0 should run 195-200* all the time, maybe 190* if you have the heat cranked.
The air was barely warm, however, I was traveling 75 MPH late at night and it was about zero degrees outside.
On a 60 degree day, the engine runs about 200 degrees and there is plenty of hot air form the heater. I just happened to be heading south from Salt Lake City late one night and my wife and I froze in the cabin when it was zero degrees outside. And, with the cooling fan running at full tilt, the engine couldn't warm up. The temp gauge was barely above the quarter mark all night.
I imagine without the fan running constantly, the temp might have risen enough to warm up the cabin.
Fan clutch, and thermostat. If the thermostat is functioning properly, until the engine reaches the thermostat temperature (195* on a stock 4.0), basically no coolant is circulated through the radiator, meaning the engine would warm up anyway. It all remains in the block. The only ways heat can be removed then are via the heater core, and heat radiating from the block (insignificant). At 75mph, there is a ton of airflow across the radiator whether the fan is on or off. Chances are, at 75mph in 0* weather, with a bad thermostat and the fan OFF, it would have been just as cold. Thermostats are fairly cheap, I'd replace it to be sure.