1. Before tearing into the heater’s mechanicals, we opted to inspect the electrical system on this ’68 fastback, as the main complaint was no blower fan operation. The electrical circuit for the heater’s blower motor is quite basic. Switched 12-volts from the ignition switch powers the heater’s fuse in the fuse box and then the circuit continues to the blower motor via the brown wire at the motor and then from the motor to the resistor block via the yellow wire. A quick check of the system can be made with a test light at the resistor block yellow wire below the glove box.