Radiator Fan shuts off even if AC is on.


New Member
Feb 4, 2007
I have a 1998 Ford Mustang Cobra 4.6 with a DOHC. When I run the AC is really lugs the motor, but that might be normal or a separate issue. The main problem is that, when I turn on the AC the Radiator Fan turn on as it should, but then after a while it turns off and the car overheats. I've replaced the Temp Sensor on the Passenger Side of the Radiator Bypass Pipe and the Thermostat. When I shut the car off and start it up again, the Fan will run and then turn off again. I've replaced the Fan Assembly last year. I don't think there's air in the system. Why wound't the fan stay on? Is there a computer that thinks the AC isn't on or thinks the engine is running cool and it isn't needed?

Thanks for any help anyone can give me concerning this problem?
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SN Certified Technician
Aug 14, 2009
Houston Texas
The low speed fan runs when the AC is on. Further there's an automatic resetting circuit breaker that protects the low speed fan.

Are you interested in an educated guess? How about bad cooling fan bearings causing excessive current draw? This causes the CB to trip while the low speed fan is running. After a short cool off delay, the CB resets and the LS fan runs for period of time. Wash, rinse, repeat.

The fact that the AC lugs the motor could be a reflection of the excessive current draw loading down the alternator.

The low speed fan circuit breaker is located in the small fuse box right hand side engine bay by the shock tower. One way to confirm the diagnosis is to test the CB for an open when the problem is occurring. Also helpful to see if the fan spins freely. If not, this indicates bad bearings.
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