Under the hood, passenger side firewall, not far from the blower motor.
In the truck!
Yes, located in the blower motor resistor pack. Follow the wires backward from the blower motor to find it.
First locate the resistor, it should be under the hood, on the firewall, passenger side, near the blower motor. Unplug the electrical connection, remove the small screws holding it in place then wiggle the resistor out.
Right next to the blower motor
In a 1988 Chevy 2500, the blower motor resistor can be found on the passenger side. It usually is behind the glove box.
The blower resistor controls the speeds of the blower motor Hi-resistance lower motor speed Lo-resistance higher motor speed
You didn't mention what model you have but if it's a full size pickup the resistor is located on the passenger side just above the foot area next the the blower motor. Two small screws (5.5mm) hold it in place.
The 2005 Ford F1 50 pickup truck blower motor resistor pack can be found on the firewall in the engine compartment. The blower motor resistor pack is on the passenger side of the firewall.
Under the hood. In the blower motor harness connector.
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.
Should be behind the glove box. The blower motor speed resistor is located under the hood, on the firewall, passenger side, close to the blower motor.
I think you should look at your fuse panels and see if you have a blown fuse . Some vehicles have a fuse for high and low blower speeds. Your problem is either the blower motor switch itself or a defective Blower Motor Resistor Pack. More than likely the Resistor Pack is defective.