Heating and Air Conditioning: Description and Operation

System Outline
Current is applied at all times through the HEATER fuse to TERMINAL 5 of the HTR relay.

When the ignition SW is turned on, the current flows through the GAUGE fuse to TERMINAL 2 of the HTR relay to TERMINAL 1 to TERMINAL 6 of the blower SW.

1. Heater Blower Motor Operation
- Low speed operation
When the blower SW is moved to LO position, the current flows to TERMINAL 6 of the blower SW to TERMINAL 5 to GROUND, causing the HTR relay to turn on. This causes the current flows from the HEATER fuse to TERMINAL 5 of the HTR relay to TERMINAL 3 to the blower motor to the blower resistor 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 6 of the blower SW to TERMINAL 5 to GROUND, causing the HTR relay to turn on. This causes the current flows from the HEATER fuse to TERMINAL 5 of the HTR relay to TERMINAL 3 to the blower motor to the blower resistor to TERMINAL 2 of the blower SW to TERMINAL 5 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 flows through the HTR relay to the blower motor to the blower resistor to TERMINAL 1 of the blower SW to TERMINAL 5 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 6 of the blower SW to TERMINAL 5 to GROUND, causing the HTR relay to turn on.

This causes the current flows from the HEATER fuse to TERMINAL 5 of the HTR relay to TERMINAL 3 to the blower motor to TERMINAL 4 of the blower SW to TERMINAL 5 to GROUND, rotating the blower motor at high speed.

2. Air Conditioning Operation
When the blower SW is set on, the current flows from the HEATER fuse to the HTR relay (Point side) to the A/C fuse to the TERMINAL 10 of the A/C SW and TERMINAL 2 of the defroster mode SW. If the A/C SW or the defroster mode SW is turned on, at this time a signal is input into the engine control module. This activates the engine control module and M/G CLT relay. So that current flows from the A/C fuse to M/G CLT relay (Point side) to A/C magnetic clutch. Causing the compressor to operate.