Electric Wiring Diagram for the Air Conditioner and Heater System of a BMW 3 series

The air conditioning and heating system in a BMW 3 series consists of several components, including the air conditioning compressor, the heater blower motor, the climate control panel, and various sensors and switches.

  1. Control knob backlight
  2. LED III
  3. LED II
  4. LED I
  5. Heater (air conditioner evaporator) fan switch
  6. 13-pin connector that connects the heater wiring to the central wire harness
  7. Connector that connects the front wiring section to the heater control panel
  8. Heater fan fuse
  9. Fuse (activates 2nd speed of heater fan)
  10. Fuse for interior lighting circuits, reverse signal, tachometer, and mirror drive mounted on the distribution block
  11. Fan temperature sensor (91°C, 1st speed)
  12. Fan temperature sensor (99°C, 2nd speed)
  13. Air conditioner switch
  14. Heater valve
  15. Evaporator thermostat
  16. Air conditioner control module (on the heater control panel)
  17. Contact connector for additional fan wiring
  18. Relay for 2nd speed of additional fan (mounted on the distribution block)
  19. Relay for 1st speed of additional fan (mounted on the distribution block)
  20. Moisture separator pressure sensor
  21. Not used
  22. Heater radiator fan
  23. Evaporator fan
  24. Contact connector for high pressure moisture sensor wiring and compressor electromagnetic clutch
  25. Temperature sensor (mounted in the evaporator)
  26. Temperature sensor (mounted in the heater)
  27. Cabin temperature sensor (located on the left side under the lower interior trim panel)
  28. Compressor electromagnetic clutch
  29. Additional fan

The air conditioning compressor is powered by a belt connected to the engine and is controlled by the air conditioning clutch relay. The compressor pumps refrigerant through the system, cooling the air that is blown into the cabin.

The heater blower motor is located in the passenger compartment and is responsible for blowing hot air from the engine’s cooling system into the cabin. The blower motor is controlled by the heater blower motor resistor, which varies the speed of the motor based on input from the climate control panel.

The climate control panel is the main interface between the driver and the air conditioning and heating system. It includes buttons and switches for adjusting the temperature, fan speed, and air flow direction.

Various sensors and switches, such as the coolant temperature sensor and the pressure switch, provide input to the climate control panel, allowing it to adjust the air conditioning and heating system based on the driver’s preferences.

Overall, the electric wiring diagram for the air conditioner and heater system of a BMW 3 series is a complex document that requires a good understanding of automotive electrical systems to properly diagnose and repair any issues.

Author: delfi

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