[cmorgan]

I own a 1999 Grand Cherokee Laredo 4.0L and it has an electric cooling fan. I have been working on its overheating problem for months now. Over the summer I narrowed the problem down to a bad water pump and a bad fan motor. I replaced them both and everything worked great for 4 months and then began overheating again.

The overheating is being caused once again by the fan not running. Everything else seems to be working fine... the upper radiator hose gets hot once the engine warms up(thermostat working), no leaking from the water pump weep hole, etc.

Since this has been a long standing problem the Jeep has on two occasions overheated a bit while stuck in traffic. Because of this I decided I should go ahead and replace the Coolant Temperature Sensor, figuring that maybe this was why the fan was not switching on and that it had gone bad by being overheated.

Now the fan still won't kick on, but I tested for voltage at the fan connector when the engine gets right above operating temp. The reading jumps to about 14 volts, so it seems that once again the fan motor must be the culprit.

Sorry for the long intro but I wanted to avoid everyone telling me that it was the Fan Relay, because according to my understanding that is not the problem... please give me a detailed explanation if i am wrong on this.

Is there any logical reason why a fan motor would fail so quickly, it just seems strange to lose 2 fan motors in one year. Am I missing something really obvious here. Any help would be much appreciated. I sick of being scared of traffic jams.

[perfectcircle]

You can run the fan right to the battery to see if the motor is indeed shot, but search the topic and you'll see a link i posted about upgrading to a mech fan. Would have saved you a lot of time, money, and headaches.