How long is the fan running for after you turn off your car?
The cooling system fan may be designed to run after the motor is turned off, to avoid excessive heat sink.
Check your owners manual for details. There may be a warning sticker under the hood alerting you to the potential of the fan starting without warning.
To diagnose this the fan relay is the place to test. The relay is conceptually two circuits. One high current circuit and one low current circuit. The concept is that the temperature sensor tells the computer that the temperature requires the cooling fan to come on. The computer then either grounds the low current circuit or feeds it with voltage. This closed circuit then completes the high current side of the relay, which runs the fan.
So your fan continues to run for one of two reasons.
1. If you find that the low current circuit is open (meaning no current flow), yet the high current side is still closed, then you have a bad relay.
2. If you find that the low current circuit is closed, it is because the temperature sensor is bad, causing it to tell the computer the engine needs cooling after the temp drops below the range when cooling is needed.
You may need a new relay that runs the fan,if the fan runs all night the car won't start.Take one of the battery cables off at night until you solve the problem.
Testimonial: "Im so thankful....it worked I just took one of the cables off...thanks"
No,you need to change the cooling fan relay,it is stuck.
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