Air Conditioning (A/C) - K Series and KV6

Description
The air conditioning (A/C) system will only operate when the engine is running. The A/C system is switched on and off by pressing the switch mounted on the center console. When the switch is pressed, an LED mounted within the switch illuminates to inform the driver the system is operational.

The position of the rotary heater control determines the amount of warm air from the heater matrix blended with cool air from the A/C evaporator, and hence the temperature of the air output from the heater ducts.

NOTE: The blower switch must be in at least position 1 for the A/C system to operate.

The A/C system is automatically switched on when either the screen or screen/feet positions are selected via the rotary distribution control knob.

NOTE: The A/C LED will not illuminate under these conditions.

Operation
Feed from the positive battery terminal (C0192) is supplied to fusible link 1, fusible link 5, and the main relay (C0632) on an R wire. All are located within the engine compartment fuse box.

The earth path for the main relay coil (C0576 on K Series vehicles, C0578 on KV6 vehicles) is controlled by the Engine Control Module (ECM) (C0913 on K Series vehicles, C0371 on KV6 vehicles) on a WK wire. The energised main relay provides a feed to fuse 4, which is also located in the engine compartment fuse box.

Fusible link 1 is connected in series with fuse 8, fuse 9 and fusible link 2, which are also located in the engine compartment fuse box. Fuse 8 (C0576) provides a constant battery feed to the blower relay (C0153) on a GN then GW wire. Fuse 9 provides a constant battery feed to the compressor clutch relay, which is also located in the engine compartment fuse box.

Fusible link 2 (C0571) is connected to the ignition switch (C0028) by an NR wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch to fuse 4 of the passenger compartment fuse box (C0588) on an SU wire. Fuse 4 (C0585) provides an ignition feed to following on G then LGS wires:
- The blower motor switch (C0058).
- The fresh/recirculated air switch (C0750).
- The fresh/recirculated air motor (C0006).

A/C Master Switch
When the blower switch (C0058) is turned to position 1 or higher, it provides a feed to the A/ C master switch (C0275) and the A/C microswitch (C2575) on SW then B wires. If A/C is requested, the switch (C0275) provides a feed to the instrument pack (C0233) via the microswitch (C2575) on a B then SK wire. When the instrument pack receives an A/C request from the switch, it informs the ECM (C0913 K Series vehicles, C0371 on KV6 vehicles) via the CAN BUS on YN (Low) and YB (High) wires. The A/C master switch is mounted on the center console, and is earthed (C0275) on a B wire.

A/C Microswitch
The A/C microswitch (C2575) is mounted on the rear of the heater distribution control knob, and switches the A/C on automatically when the screen or feet/screen position is selected. In this instance the switch contacts close, allowing the blower motor switch (C0058) to provide a feed to the instrument pack (C0233) on an SW then SK wire, by-passing the A/C master switch.

Compressor

K1.8
When the ECM (C0913) receives an A/C request signal via the CAN BUS, it will energise the compressor clutch relay by providing an earth path for the relay coil (C0576) on a UB wire. A feed from fuse 9 of the engine compartment fuse box is now able to flow across the energised relay (C0578) to the compressor clutch (C0127) on an R wire.

KV6
When the ECM (C0371) receives an A/C request signal via the CAN BUS, it will energise the compressor clutch relay by providing an earth path for the relay coil (C0578) on a BR wire. A feed from fuse 9 of the engine compartment fuse box is now able to flow across the energised relay (C0575) to the compressor clutch (C0127) on an R wire.

Pressure Sensor
The pressure sensor is located in the high pressure A/C line adjacent the compressor, and replaces the more traditional trinary pressure switch. The ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) provides a 5 V reference voltage to the pressure sensor (C1257) on a UO wire. The pressure sensor (C1257) is provided an earth path by the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) on a PB wire.

The pressure sensor (C1257) provides the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) a signal feed on a UG wire. The value of this signal feed is dependent upon the pressure within the A/C system. The ECM uses this feed to determine the pressure within the A/C system, enabling it to carry out the following tasks:
- To provide a safety cut-out function if the pressure within the A/C system goes either too high or too low.
- To control the speed of the cooling and condenser fans via the cooling fan control unit.
- To help control engine idle speed.

Evaporator Temperature Sensor
The evaporator temperature sensor is used to ensure the evaporator doesn't freeze. The ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) provides a feed to the evaporator temperature sensor on a GO wire (GU on KV6 vehicles). The sensor is provided an earth path via the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) on a BO wire (PB on KV6 vehicles).

NOTE: The ECM also uses the evaporator temperature sensor signal in conjunction with the pressure sensor signal to help control engine idle speed.

Cooling Fan Control Unit
Fusible link 5 of the engine compartment fuse box (C0573) provides a constant battery feed to the cooling fan control unit (C0208) on an NG wire. Fuse 4 of the engine compartment fuse box (C0575) provides a feed to the cooling fan control unit (C1680) on an NK wire when the main relay in energised. The cooling fan control unit (C0208) is earthed on a B wire.

To control cooling fan and condenser fan speed, the ECM (C0913 on K Series vehicles, C0371 on KV6 vehicles) provides the cooling fan control unit (C1680) a Pulse Width Modulated (PWM) signal on a UW wire (UR then UW on KV6 vehicles). The frequency of the pulses supplied by the ECM determines the speed the cooling fan control unit will drive the cooling fan and condenser fan motors.

The cooling fan control interprets the PWM signal provided by the ECM as follows:
- If a PWM signal of between approximately 12 % and 87 % is received by the cooling fan control unit , it will not power the cooling fans.
- If a PWM signal of 87 % or over is received by the cooling fan control unit, it will provide a feed to the cooling fan (C0005) and condenser fan motors (C0280) on SU wires. An earth path is provided for the cooling fan (C0005) and condenser fan motors (C0280) by the cooling fan control unit (C2470) on a pair of PS wires.
- If a PWM signal of less than 12 % is received by the cooling fan control unit, it assumes a fault has occurred and powers the cooling and condenser fan motors as described above.
- If a continuous voltage is received by the cooling fan control unit, it assumes a fault has occurred and powers the cooling and condenser fan motors as described above.

Fresh/Recirculated Air
Fuse 4 of the passenger compartment fuse box (C0585) provides an ignition feed to the fresh/recirculated air motor (C0006) and the fresh/recirculated air switch (C0750) on G then LGS wires. When the switch is the normal (released) position, it provides an earth path for the motor (C0006) via a Y wire. The motor will open the recirculation flap, allowing the A/C system to use air drawn from outside the vehicle.

If the fresh/recirculated air switch is pressed, it provides an earth path for the motor (C0006) via a K wire. The motor will now close the recirculation flap, allowing the A/C system to use recirculated air. The switch is mounted on the center console, adjacent the A/C master switch, and is earthed (C0750) on a B wire.