MY heater fan works on 4 & 5 Only on my 2000 Silverado

there is a relay in heater box go to autozone they can get you one and let you know where it is located

you can test the motor with a multe tester with ohms capable, locate the heater motor and the wires feeding it there will be 2 find the plug and unplug it, using the tester probe the 2 wires with the red and black from the meter to the motor side, on ohms scale the meter should deflect close to full scale, with a digital it should read around 30 or have at least have a low number but no lower than 20 or so, if you get a reading your motor is probably OK, you can also use the meter in voltage mode and with the heater turned on you should read a voltage higher than 10 on the vehicular side of the plug, if there is no voltage there check to see if you have voltage at the heater fuse, if so than replace your fan control switch,,,good to go

air recir actuator motor shorted you can reach between blower motor and heater case and unplug a pain to replace

SPEED CONTROL IS BAD NEED TO REPLACE

I would replace the blower resistor first. its down by the blower motor.

no this is not a thermo issue the heater controls are bad and need to be replaced ive seen this alot in general motor trucks and cars.thanks and good luck

You probably need to change the heater blower motor.

Check the relais module located inside under the rh side of the heather box you can see the connector most of them need to be replaced as they burn out you may need to replace the blower motor as well,high amp draw caused by faulty bearings will overload the blower motor controller

replace the motor it is burned up

replace the blower motor .,....