PROJEKT36 · WIRING

Heating & climate

The blower relay every car has, the IHKA automatic climate control with its compressor relay, the simpler heater fitted to cars without A/C, and the heated rear window. Hover or tap a row to see where the wire goes.

Standard petrol E36 from the 1998 BMW wiring manual. Independent (parked) ventilation left out. On a phone, scroll the diagram sideways.

projekt36.com/wiring/heating-climate/

SW blackRT redGN greenBL blueGE yellowBR brownWS white GN/SW = green with black stripe supply / ground of a part shown elsewhere

Blower relay K4 (all cars)

fuse F20 30A 0.35 GN ignition switch X209 pin 1 ground X173 2.5 GN/BR IHKA output stage / blower switch K4 Heating blower relay heating blower relay, X58 30 Blower supply 86 Coil supply (15) 85 Coil ground 87 Blower feed

How it works

The blower always runs from fuse F20 through relay K4, which pulls in with the ignition on. After that the IHKA output stage or the HR blower switch sets the speed.

Redrawn from BMW ETM 6410.5 and 6450.7 (05/99), standard petrol E36 (316i–328i); diesel and M3 parts are left out.

IHKA climate control X1527

fuse F31 5A fuse F23 5A 0.5 BR ground X10012 0.5 BR ground X10012 0.5 BL sensor B13 X774 pin 1 0.35 GR sensor B14 X771 pin 1 0.35 GE/RT sensor B11 X772 pin 1 0.35 GE/BL sensor B12 X773 pin 1 0.35 BR/OR all four sensors, pin 2 0.35 SW/WS cluster X17 pin 2 0.35 SW DME, via X20 pin 20 0.5 GR/RT light switch 58g 0.35 SW/GN starter 30h, splice X276 0.35 BL/SW pressure switch B8y pin 1 0.35 VI/GR DME, via X20 pin 6 0.35 BR/GE defogger relay K13 pin 85 0.5 GE/VI water valve Y4 X85 pin 2 0.5 GE/BR water valve Y4 X85 pin 3 0.35 WS M36 X663 pin 4 0.35 BL M36 X663 pin 3 0.35 GR M36 X663 pin 2 0.35 GE M36 X663 pin 1 0.35 BL/RT output stage N2 X671 pin 3 0.35 SW/WS/GE BC X1071 pin 14 0.35 GN/BR relay K450 X607 pin 6 0.35 WS/VI diagnostic link X1527 Climate control unit IHKA control unit A115 25 Battery (30) 24 Ignition (15) 21 Ground 23 Ground 1 Outside temperature 2 Evaporator temperature 3 Left heater temperature 4 Right heater temperature 22 Sensor ground 5 Road speed 6 Engine speed (TD) 7 Lighting 9 Cranking (50) 11 A/C compressor request 10 Idle speed increase 12 Rear window defogger 18 Left water valve 13 Right water valve 14 Fresh air flap motor 15 Fresh air flap motor 16 Fresh air flap motor 17 Fresh air flap motor 19 Blower speed 8 Output to on-board computer 20 Independent ventilation 26 Diagnosis TxD

How it works

The IHKA reads four temperature sensors, road and engine speed, and drives the two water valves, the fresh air flap, the blower output stage and the other flap motors over the three-wire Mi-bus.

It does not switch the A/C compressor itself: it asks through the pressure switch (pin 11) and the DME switches the compressor relay, raising the idle (pin 10) first.

Redrawn from BMW ETM 6450.7 (05/99), standard petrol E36 (316i–328i); diesel and M3 parts are left out. Not covered: X1558 (AUC air-quality sensor B414: pins 1–3, 0.5 mm² blue, brown and yellow to X3211; sensor pin 4 to ground X10010); the Mi-bus plug (0.35 mm² red, brown and yellow, daisy-chained to the defroster, ventilation, footwell and recirculation flap motors M35, M44, M46, M40).

A/C compressor relay K19

fuse F39 7.5A fuse F16 5A 0.5 SW/BL DME, via X20 pin 4 0.75 SW/RT/GE solenoid clutch Y2 X163 pin 1 K19 A/C compressor relay A/C compressor relay, X51 30 Clutch supply 86 Coil supply (15) 85 Coil ground (DME) 87 Compressor clutch

How it works

The A/C clutch is powered from F39 through relay K19. The DME grounds the relay coil once the IHKA request has passed the pressure switch.

Redrawn from BMW ETM 6450.7 (05/99), standard petrol E36 (316i–328i); diesel and M3 parts are left out.

Heater without A/C (HR): temperature regulator

0.5 GN/GE fuse F23 5A ground X10010 0.5 BR/OR water valve Y4 X85 pin 3 0.5 BR/SW sensor B11 X772 pin 2 0.5 BR/OR sensor B11 X772 pin 1 0.5 GR/RT light switch 58g 0.5 BR/WS defogger relay K13 pin 85 X899 Temperature regulator temperature regulator A32y 1 Ignition (15) 6 Ground 3 Water valve 2 Heater temperature sensor 7 Sensor return 5 Lighting 4 Rear window defogger

How it works

Cars without A/C have the simpler heating control: one water valve, worked by the temperature regulator from one heater sensor, and a four-speed blower switch.

Redrawn from BMW ETM 6410.5 (05/99), standard petrol E36 (316i–328i); diesel and M3 parts are left out.

Heater without A/C (HR): blower switch and resistor

2.5 GN/BR blower relay K4 pin 87 2.5 GN/GR blower motor M30 X816 pin 2 2.5 BL ballast resistor R11 pin 1 1.5 GN ballast resistor R11 pin 2 1.5 SW ballast resistor R11 pin 3 2.5 GN/GR blower motor M30 X816 pin 2 X905 Blower switch blower switch S75 (HR) 5 Feed from K4 4 Stage 4 (full) 3 Stage 3 2 Stage 2 1 Stage 1 R11·4 Resistor output

How it works

Stages 1–3 run the blower through the ballast resistor; stage 4 bypasses it. Only stage 4 working means a blown thermal fuse in the resistor.

Redrawn from BMW ETM 6410.5 (05/99), standard petrol E36 (316i–328i); diesel and M3 parts are left out.

Rear window defogger K13

fuse F6 30A fuse F23 5A 0.5 BL/SW IHKA pin 12 / HR X899 pin 4 2.5 SW antenna amplifier N8 X379 pin 1 K13 Rear defogger relay rear defogger relay, X292 30 Heater supply 86 Coil supply (15) 85 Coil ground (button) 87 Rear window heater

How it works

The heated rear window also works as the radio antenna, so its feed runs through the antenna amplifier. The button in the climate panel only grounds the relay coil.

Redrawn from BMW ETM 6424.0 (05/99), standard petrol E36 (316i–328i); diesel and M3 parts are left out.

Reading the wire codes

BMW labels every wire with its size and colour, for example 2.5 SW/GE: 2.5 mm², black (schwarz) with a yellow (gelb) stripe. Connectors are numbered X…, followed by the pin. The wires in these diagrams are drawn at relative thickness, so the 25 mm² battery cable stands out from a 0.35 mm² signal wire.

Codes used here: SW = black, RT = red, GN = green, BL = blue, GE = yellow, BR = brown, WS = white.