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George H.
George H., ASE Certified Technician
Category: Ford
Satisfied Customers: 15627
Experience:  ASE Master Tech 15+ Years
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Ford F250 SuperDuty Pickup 4x4: the heater fan will not shut

Customer Question

the heater fan will not shut off when the ignition switch is turned off
Submitted: 2 years ago.
Category: Ford
Expert:  George H. replied 2 years ago.

Hello I will help you with your question,

 

What year is your truck?

 

 

Customer: replied 2 years ago.

2000

 

Expert:  George H. replied 2 years ago.

The motor is grounded through the blower switch on the controls and the mode switch controls the relay that gives power to the motor so when you turn the mode to off the relay opens but the blower speed switch is shorted so the blower runs at all times.

 

Now the blower switch never turns the motor off all the way, the motor is only off when the ignition is turned on if you turn the mode switch to off. This is positive ventilation to keep the cab pressurized.

 

Does the motor turn off with the key? If it does it sounds like normal operation.

 

Let me know what you are seeing so I can help

 

Thank you

 

\

 

Customer: replied 2 years ago.
the blower turns off with the controls but does not turn off with the ignition
Expert:  George H. replied 2 years ago.

OK, then the power from the ignition to fuse 22 in the central junction box is not shutting off with the ignition switch.

 

This comes directly from the ignition switch on the green/yellow strip wire so it looks like the switch is failing to disconnect. Try pulling fuse #20 in the battery junction box. This is a 50 amp square fuse that will be hard to remove. If the blower then turns off the ignition switch needs to be replaced.

 

Let me know how I can help you

 

Thank you

 

 

Customer: replied 2 years ago.
fuse #20 and 21 shows for the ignition and neither killed the fan but #22 junction box battery feed did shut it off
Expert:  George H. replied 2 years ago.

Fuse #22 will shut it off as it is the feed to the relay.

 

If #20 nor #21 did not shut it off there is a cross feed in the harness or the fuse block.

 

Is there any aftermarket equipment installed in this truck?

 

 

 

 

Customer: replied 2 years ago.

no

 

Expert:  George H. replied 2 years ago.

OK, the only power to this circuit is supposed to come through the ignition switch, did you remove the 20 and 21 fuses one at a time or together?

 

If it was one at a time try both at once.

 

Let me know which way you did it.

 

Thanks

 

 

Customer: replied 2 years ago.
1 at a time i will go try both together
Expert:  George H. replied 2 years ago.

OK, if both go out you either have a GEM module backfeeding or the ignition switch so the next step would be to unplug the GEM.

 

Let me know what happens

 

Thanks

 

 

Customer: replied 2 years ago.
what is a gem
Expert:  George H. replied 2 years ago.

Generic Electronic Module (GEM) and it controls the delay functions and some of the lighting tasks.

 

Did the blower stop with both out?

 

 

Customer: replied 2 years ago.
when I went out and turned the fan control switch nothing came on. I turned the ignitionon and the fan on it came on. I turned off the ignition and everything shut off. I did not have to pull the fuses again. We did have some snow last night, could something have gotten wet to cause this?
Expert:  George H. replied 2 years ago.

Sure, any water path could have fed power to the relay and allow it to stay on. If it is working now let it go but keep turning the mode switch off or you might run those batteries down. Check on it, you probably have a failing switch but until it breaks again you can't tell.

 

Let me know how I can help you

 

Thank you

 

 

George H., ASE Certified Technician
Category: Ford
Satisfied Customers: 15627
Experience: ASE Master Tech 15+ Years
George H. and 15 other Ford Specialists are ready to help you
Customer: replied 2 years ago.
thank you
Expert:  George H. replied 2 years ago.

Glad to help and if it acts up again come back, I will be happy to continue to help

 

Thanks

 

 

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