Heating and Air Conditioning: Description and Operation

SYSTEM OUTLINE

1. HEATER BLOWER MOTOR OPERATION
Current is applied at all times through the HTR fuse to TERMINAL 5 of the HTR relay.
When the ignition SW is turned on, the current flows through HTR fuse to TERMINAL 1 of the HTR relay to TERMINAL 2 to TERMINAL 8 of the blower SW.

- Low speed operation
When the blower SW is moved to LO position, the current flows the to TERMINAL 8 of the blower SW to TERMINAL 1 to GROUND, causing the HTR relay to turn on. This causes the current to flow from the HTR fuse to TERMINAL 5 of the HTR relay to TERMINAL 3 to TERMINAL 1 of the blower motor to TERMINAL 2 to TERMINAL 1 of the blower resistor to TERMINAL 4 to GROUND, rotating the blower motor at low speed.

- Medium speed operation (Operation at M1, M2)
When the blower SW is moved to M1 position, the current flows to TERMINAL 8 of the blower SW to TERMINAL 1 to GROUND, causing the HTR relay to turn on. This causes the current flows from the HTR fuse to TERMINAL 5 of the HTR relay to TERMINAL 3 to TERMINAL 1 of the blower motor to TERMINAL 2 to TERMINAL 1 of the blower resistor to TERMINAL 2 to TERMINAL 6 of the blower SW to TERMINAL 1 to GROUND. At this time, the blower resistance of the blower resistor is smaller than at low speed, so the blower motor rotates at medium low speed.
When the blower SW is moved to M2 position, the current through the motor flows from TERMINAL 1 of the blower resistor to TERMINAL 3 to TERMINAL 5 of the blower SW to TERMINAL 1 to GROUND. At this time, resistance of the blower resistor is smaller than at M1 position, so the blower motor rotates at medium high speed.

- High speed operation
When the blower SW is moved to HI position, the current flows to TERMINAL 8 of the blower SW to TERMINAL 1 to GROUND, causing the HTR relay to turn on.
This causes the current to flow from the HTR fuse to TERMINAL 5 of the heater relay to TERMINAL 3 to TERMINAL 1 of the blower motor to TERMINAL 2 to TERMINAL 4 of the blower SW to TERMINAL 1 to GROUND, rotating the blower motor at high speed.