Blower speeds on ac/heater for 2003 chevy pickup(v6)

A/c compressor works fine and the blower motor works and shutdown right? it is the problem with the blower resistor or with blower motor relay. try to direct the resistor irrespective of the speed. hope the problem may be solved.

you should make a diagnostic to know what happened to your car
of course you need an auto diagnostic tool : http://www.chinasnoy.comand you can find all kinds of tools in chinasinoy.com

Likely the blower motor resistor. located right next to the blower motor, this device is resposible for reducing the voltage suplied to the motor. when it fails you may loose some or all speeds of the motor

I’m happy to assist further over the phone at https://www.6ya.com/expert/samuel_dda9c48bb7ffbfd3

the blower speed setting is the cause by the blower resistor

The resistor is most likely bad but should still work on the highest setting.Would check pigtails to the resistor and to the blower motor for burnt or discolored wiring.You can try tapping the blower motor and wiggling the wiring harness too see if it will work on the highest setting. It is possible that the blower motor is bad as well typically when you lose the speed selection it is the resistor but you should always have high speed.

Sometimes the electrical connecter burns on the back side of your switch. You can get just the switch and replace it and repair the connecter when possible.

you have a bad blower motor resistor

needs blower control module

REPLACE A/C BLOWER RESISTOR.

you will need to replace the fans blower resistor. its mounted in the cab. in the lower right side of the heater box. some aftermarket suppliers are carrying the part but all chevy or gmc dealers will have it.
good luck chris