Check fuse and connections, ensure battery is charged. With transmission in Park, turn ignition switch to On. Locate blower motor, release wiring harness. Connect voltmeter to blower motor connector, move switch through each position, noting voltage readings. If voltage but motor doesn't work, connect jumper wire between motor ground and chassis ground, and fused jumper wire between battery positive and motor positive. If no voltage, remove resistor block connector and check for voltage. If voltage, check resistor block for continuity and wiring for open/short. If no voltage, remove heater control panel and check for voltage at blower motor switch connector. If voltage, connect jumper wire between switch connector and resistor block terminals. If motor operates, replace switch.