coolant fan

I have a 2001 Plymouth neon and the coolant fan cuts on and off about every 30 seconds . Anyone know what the problem could be ?

Two things I would look at - based on my having owned a 97 Neon for a couple of years. First, is the a.c. system on? If you are using the defroster and have the heater fan on, the a.c. compressor is also supposed to run. But if its low on freon, the compressor will cycle off shortly after coming on - and the radiator fan (or fans) may be cycling on when the a.c. compressor is on, and off when the compressor cycles off. This would repeat and repeat, etc.
Secondly; I think the fans are made to run by a circuit that 'pulses' the voltage to the fans, to make them run at low to high speeds, as needed. Its a pulsed goody where the pulses get wider for a higher duty cycle, and if its dying - it may be turning the fan on now and then, instead of regulating the fan to keep the engine cool as it should. On mine that TDM (time division multiplexing) module was mounted to the sheet metal next between the radiator and the headlamp. The only time I could see it well was the time I had the engine and transmission out of the car.
Good Luck.....

Secondly; I think the fans are made to run by a circuit that 'pulses' the voltage to the fans, to make them run at low to high speeds, as needed. Its a pulsed goody where the pulses get wider for a higher duty cycle, and if its dying - it may be turning the fan on now and then, instead of regulating the fan to keep the engine cool as it should. On mine that TDM (time division multiplexing) module was mounted to the sheet metal next between the radiator and the headlamp. The only time I could see it well was the time I had the engine and transmission out of the car.
Good Luck.....
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