Replace the high speed relay.
The blower motor resistor pack is defective. Replace it.
The blower resistor on a 1999 Chevy truck Z1500 is located behind the glove compartment. There is also a resistor on the firewall next to the blower motor itself.
In the truck!
First, take a socket wrench to remove the cover of the blower motor of a 1993 Chevy truck. Then pull the motor blower out and install a new one in its place. Lastly, screw the bolts of the blower motor cover back in.
The fusebox which controls the blower motor is under the hood up by the firewall.
what is initial timing on 1966 chevy 250
Under the hood, passenger side of firewall,
Defective blower motor switch, or defective blower motor resistor pack.
1999 S10, it should be under the hood, on the firewall, on the passengers side, close to the blower motor.
behind the glove compartment, to the left
You will have to replace it. The bearings are worn out in the blower motor.
You gotta start by figuring out what's wrong with it. You need to determine if it's the blower motor itself, or the power supply, then troubleshoot to determine the exact cause.