My 02 500 either stalls or runs rough when the fan kicks on. If it does stall I have a real low spark on the plug when using the starter and it wont start. I can get it to start with the pull start. My first thought is a bad ground on the fan circuit? Any suggestions would be great.

 

Check the voltage of the battery.Shoud be around 12.5 volts or so,If not then charge the battery and check the operation of the machine.When running and at above idle{1200 to 1500RPMs}the battery voltage should be around 13.5 volts.
If voltages are correct then start looking for grounding issues.
Running the machine with a bad battery can fry the stator.

 

THanks....all the volltage readings are good, I will check grounds to see if I can identify the problem.

 

what's the voltage at battery terminals when the fan is running and making the engine run rough?...

look on the load side of the thermal switch for a rub thru and grounding out... problem sounds to be aft the thermo sensor... tj

 

also could be the fan is dragging so hard. the fan might be work out and pulling way to much power as well. imo

 

Try to check the amp draw when the fan starts...its a voltage related problem...