Classic/Antique Car Repair: 1970 impala a/c blower not working, jumper wire, test light

Question
I read your post about you blower not working. I'm having a similar issue. My blower isn't working but my compressor responds to the controls. I changed the a/c fuse and still no blower...... Can you assist with a possible resolution to this problem?

Answer
There are several items that could cause this problem. First is the blower motor itself. there is one connection on the blower that is hot (voltage present) when the system is on and the blower switch is on. To check the motor I usually make up a jumper wire and connect the motor to the POS terminal of the battery. If the motor is ok it will run when jumped. If the motor is ok then the problem is the relay, the resistor, or the switch on the dash. The first step to check is to disconnect the wire at the motor, turn the system on at the dash and use a voltmeter or test light to check for voltage at the wire. If there is no voltage then it is time to get a wiring diagram from a manual and follow the circuit back through the switch, relay, and resistor.
Brad