You may want to include make and model, depending on the year some are vacuum operated and so forth. You may get more replies if you include that information, Also simply check the fuse first. If not you can remove the panel and make sure there is power going into the switch, if so next see if there is power leaving the switch. It is a matter of finding where the break in power is...
Your blower switch sensor is out. Replace it!Then all the speeds will work
The wiring, switch or blower has failed.
either the blower control switch or the blower motoer needs replacing
If you are saying the blower motor will not work, then check the fuse. If the fuse is not blown, then it is possibly a defective Blower Motor Resistor Pack, blower motor, or blower motor speed control switch, in that order.If you are saying the blower motor will not work, then check the fuse. If the fuse is not blown, then it is possibly a defective Blower Motor Resistor Pack, blower motor, or blower motor speed control switch, in that order.
switch contact"s
did your heater switch go out all of a sudden or did some work like high work and low not work? if some worked your blower resister is most likely bad under your glove box
bad resistor
Blown fuse, bad blower motor switch, blower motor itself, or a defective blower motor resistor pack.
Check the blower motors ground and power in the truck and the blower motors resister......
Either your switch is messed up, or more likely the blower motor resistor is bad.
Check your radiator fan switch and your fan switch coolant sensor .
You need to replace the blower motor resistor. I've been there done that.