[bustedknuckles]

My blower motor only comes on at high, doesnt matter if im running heat or a/c it only works on high...

any one have any ideas?

[mutlyi4]

blower motor resistor went bad ?

[03SonicBoom]

Blower motor resistor is bad. I would bet big money on it. Cheap and easy to replace part.

[03_StangGuy]

Is this typical sign on most or all cars?? I have that happen on my vw and it was the resistor and my moms trailblazer is doing the same thing. Thought it might be the resistor but I wasnt sure since I never worked on a chevy.

[bustedknuckles]

the resistor limits the voltage that travels through the circuit for different fan setting so when it goes bad it wont limit the voltage at all thus only working on high.... i think lol

[03SonicBoom]

Originally Posted by bustedknuckles the resistor limits the voltage that travels through the circuit for different fan setting so when it goes bad it wont limit the voltage at all thus only working on high.... i think lol

Kind of how it works. There are 4 settings on the blower knob and I'll call them 1, 2, 3, and 4 (1 being "low" and 4 being "high"). When the knob is set on 4, there is no resistor in the circuit and the blower motor receives 12V. When the knob is set on 3, there's 1 resistor in the circuit and the blower motor receives 10V (made up voltage). Since it's only 10V, the blower will run slower than if it received 12V. When the knob is on 2, there's 2 resistor in the circuit and the blower motor receives 8V (made up voltage). With the knob on 1 there are 3 resistors in the circuit and the motor receives even less voltage.

When the blower motor resistors burn out, they act as open circuits. Open circuits provide the blower motor with 0V. Since knob setting 4 is just a jumper across the resistor pack, there's no resistor to burn out. Sometimes you'll burn out 1 or 2 resistors and it'll only work on setting 3 and 4.

[Rocketburn11]

It's the resistors. About $20 part at most auto parts stores.

To replace it, remove the glove box (take the 3 screws out from the hinge underneath).

Then remove the resistors, it is a small plate held in with two bolts, just above the blower motor and to the left. When you have it out unplug the wires and replace it.

Problem Solved.