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 out TERMINAL 1 to TERMINAL 6 of the blower SW.

1. Heater Blower Motor Operation 

   * Low speed operation

   When the blower SW is moved to the LO position, current flows to TERMINAL 6 of the blower SW then out of TERMINAL 5 to GROUND, causing the HTR relay to turn on. This causes current to flow from the FR HTR fuse to TERMINAL 5 of the HTR relay then out 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 the M1 position, current flows to TERMINAL 6 of the blower SW and out TERMINAL 5 to GROUND, causing the HTR relay to turn on. This causes current to flow from the HEATER fuse to TERMINAL 5 of the HTR relay, out TERMINAL 3 to the blower motor to the blower resistor to TERMINAL 2 of the blower SW and out TERMINAL 5 to GROUND. At this time, the blower resistance of the blower resistor is less than at low speed, so the blower motor rotates at medium low speed.

   When the blower SW is moved to the M2 position, current flows through the HTR relay to the blower motor then to the blower resistor and then to TERMINAL 1 of the blower SW and finally out TERMINAL 5 to GROUND. At this time, the resistance of the blower resistor is less than at the M1 position, so the blower motor rotates at medium high speed.

   * High speed operation

   When the blower SW is moved to the HI position, current flows to TERMINAL 6 of the blower SW, and out TERMINAL 5 to GROUND, causing the HTR relay to turn on.

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

2. Air Conditioning Operation 

   When the blower SW is turned on, current flows from the HEATER fuse to the HTR relay (Point side) to the A/C fuse, then to TERMINAL 2 of the A/C SW. If the A/C SW is turned on, at this time a signal is sent to 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 the A/C magnetic clutch. Causing the compressor to operate.

3. DEF or FOOT & DEF Synchronized Control Function 

   When the blower SW is on and the heater control lever (Air vent mode control lever) is turned to the DEF or FOOT & DEF position, it causes the A/C to operate and the air inlet control SW to move to the FRESH position regardless of whether the A/C SW is on or not.