Chart 1C-4 Blower Inoperative at Any Speed

CIRCUIT OPERATION
The blower motor is a variable speed motor, which runs at a speed proportional to the applied voltage. The higher the voltage applied to the motor, the faster the speed.

While the ignition switch is in the "RUN" position battery voltage is applied to the heater and A/C control through fuse #17. With the heater and A/C control in the "OFF" position, no voltage is supplied to the blower motor.

When any other mode position is selected, voltage is applied to the heater and A/C control blower Switch, and blower motor resistor if not in "HI."

With the heater and A/C control "ON" the low blower relay contacts will be closed, current will flow through CKT 60 to 5264 through CKT 60 to terminal "A" of the blower motor resistor.

As the heater and A/C control blower switch is moved through positions "M1" and "M2," the switch bypasses part of the blower resistor allowing more voltage to be applied to the blower motor, which will increase its speed.

When the heater and A/C control blower switch is in the "HI" position, voltage is applied through CKT 52 to the coil of the high blower relay. The high blower relay energizes, removing the blower resistor from the circuit. Battery voltage is then applied directly to the blower motor through the high blower relay contacts. The motor runs at maximum speed.

DIAGNOSTIC AIDS
1. Check I/P Fuse 17 for open. If open, check for short to ground through CKT 641.
2. Check U/H maxifuse 10 for open. If open, check for short to ground through CKT 42.
3. Check G200 by noting normal operation of the underhood lamp or license lamp.
4. If blower motor is "ON" with ignition switch in "OFF," check for short to B+ on CKT 60, CKT 52, CKT 63, CKT 64, CKT 65, CKT 72 and CKT 101. If OK, replace high blower relay.
5. If blower motor is "ON" at all times with ignition switch in "RUN" and heater-A/C selector switch in "OFF," check for short to ignition voltage on CKT 60, CKT 52, CKT 63, CKT 64, CKT 65, CKT 72 and CKT 101. If OK, replace heater and A/C selector switch.
^ Check for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load).
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems.