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Shane, ASE Certified Technician
Category: GM
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Experience:  Master Certified with L1, two years GM dealership experience
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My heater fan will not shut off even when the ignition is off

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My heater fan will not shut off even when the ignition is off and the fuse is pulled,could it be the ignition switch?

Hello the relay in your blower motor is stuck on, there is a TSB for this issue. Replace the blower motor resistor and you'll be back in business.

Customer: replied 6 years ago.
what is a TSB and how hard is it to get at the resistor on the blower motor? Would this cause the fan to only work on #4 & #5 settings when I am not having a problem with the resistor?
Customer: replied 6 years ago.
How does the resistor get power if the fuse is pulled?

Replacing the resistor will cure both problems. TSB is a technical service bullitin seen below


Subject:HVAC Blower Motor May Run Continuously After Vehicle is Turned Off (Replace Blower Resistor Relay)

Models:2004 Chevrolet Avalanche, Silverado, Suburban, Tahoe, TrailBlazer, TrailBlazer EXT
2004 GMC Envoy, Envoy XL, Sierra, Yukon, Yukon XL
with Manual Control HVAC (RPO CJ3)
Built Prior to August, 2003


This bulletin is being revised to update the parts information. Please discard Corporate Bulletin Number 03-01-38-015 (Section 01 -- HVAC).


Some customers may comment on the HVAC blower motor running after the vehicle has been turned off. The blower may run for just a few minutes or continuously until the battery is discharged.


A new style HVAC blower relay/resistor may stick in the "on" position. When the HVAC fan blower relay has been energized, the contacts may "micro-weld" together. After this occurrence, the HVAC blower may not respond to the HVAC controller commands.


Replace the HVAC blower resistor/relay with the type used previous to the 2004 model year. The appropriate part numbers are listed in the table below. For specific repair procedures, refer to the 2004 Service Information (SI) under Blower Motor Resistor Assembly Replacement (SI Document ID #526350 (C/K) or #729996 (S/T).

Parts Information

Part Number



Relay, Blower Motor Resistor (C/K)


Relay, Blower Motor Resistor (S/T)



The blower motor fuse is in the underhood fuseblock labeled blower and it is a 40A fuse

The blower motor resistor is connected to the harness that plugs into your blower motor. It is located on the bottom side of the dash on the pass. side. remove the bottom cover it is held in by 2 screws next to the blower motor

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