blower motor on 1998 Chevrolet 3500 Pickup

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i have replaced the blower resistor on the top of the heater box and the switch(only) in the control panel. it still blows on high only. i spoke to a local dealer, they say thats all it should be. do you have any ideals what else to try.
(1) Answer
Check the connections to and from the switch and resistor. You can use a test light or multimeter to make sure the motor is seeing voltage in all of the switch positions. Make sure there is no corrosion on the connectors and that they are making good contact.
Earlier models had a service bulletin on this but all it says is to replace the resistor assembly. If you bought the parts at the dealer, you probably have the correct part based on your VIN.