2004 sierra, fan blower stopped, not the fuses. where is the fan blower switch and how do I replace

Check the A/C ,check signal to fan and ground of the resistance.(resistors )

is this the blower motor fan for you heating and A/C or the cooling fan cooling fans have a relay blower fans are fused but controlled from switches inside as well as fuses

Sounds like the blower switch is shorted. Try running through the blower speeds to see if that changes anything.

The blower relay is stuck,replace it.

The switch or the wire harness at the blower motor has gone bad. The highest setting 5 has no resistor, so the blower runs on high but the high current flow ends up burning up the switch's contact on that setting or the resistor wire harness at the blower motor has gone bad. Common would be the switch it self, if the switch is good. Then it's going to be the wire leads at the speed resistor by the blower motor under the glove box by the passenger leg compartment. Keep me posted, be glad to help you get your Sierra running 100% again soon.

Have you had the blower motor switch replaced? I had a Chevy Silverado and the low worked but no other settings. It is a pretty quick fix and reasonably cheap.

Check the blower motor speed control resistor pack is ok.
(The resistor pack is usually located in the blower fan ducting in the air flow).
Check condition of electrical connection terminals on the blower motor circuit - these terminals pass considerable current and over time may fatigue overheat and loosen.
Check operation/replace any blower motor control relay,
Check the blower motor will run if +12v directly applied to the blower motor.
Check operation of the blower motor speed control switch is ok.

Blower motor resistor is most common ($20-$70) it controls the blower motor fan and speeds or fan relay fuse (usually under the hood) If it's not either then the blower itself is bad. You can pull the motor and apply 12volts to it to test, if it spins then the resistor.

Per your description, I believe you may have a blower fan relay that is stuck closed.
Remove the relay from the under-hood fuse center and see if the fan stops.
If it does stop, put the relay in slowly and see if you here the relay "click" and the fan come back on.
Let me know.
Regards,

UNPLUG THE A/C CONNETOR ON THE A/C COMMPRESOR. REPLACE THE FUSE AND TURN ON THE SWITCH. FUSE OK . REPLACE THE COMMPRESSOR AND THE RECIVER DRIER.