PROJEKT36 · WIRING

Cooling fan

How the E36 auxiliary fan switches between normal and high speed, redrawn with the wire colours: the 1993–95 version first, then the 1996–99 relays. Hover or tap a wire to follow it; tap a part for what it does.

1993–95 from the Bentley Engine Cooling diagram, drawn for a 1994 build (colours converted to BMW's codes, no wire sizes in that source). 1996–99 from the 1998 BMW wiring manual. On a phone, scroll the diagram sideways.

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SW blackRT redGN greenBL blueGE yellowBR brownWS white GN/SW = green with black stripe supply / ground of a part shown elsewhere colour not given in the source

Auxiliary cooling fan

GN/BL X10016 · 12 RT/GN X10018 · 22 GN/RT BL SW/BL G110 SW/GN SW/GR G110 G110 SW/GR BL/SW SW/BL comp. relay P90 Front power distribution box F16 5A run and start · F41 30A always live F16 F41 Radiator Temperature switch 2 closes above 91 °C3 closes above 99 °C 3 1 2 A/C Pressure switch in the high-pressure linefan contact closes above 18 bar DME IHKA fan IHKA Climate control DME Engine control M3.1 / M3.3.1 85 48 M Auxiliary fan motor 2 = normal speed3 = high speed 1 3 2 Front power box Normal speed relay coil 4–8 · contact 6 → 2 8 4 5 2 6 Front power box High speed relay coil 8–4 · contact 6 → 2, rest 6 → 5 4 8 6 5 2

How it works

The fan has two windings: pin 2 for normal speed and pin 3 for high speed. Both relays are fed from fuse F16 on their coils and get the fan current from fuse F41 (30A).

At rest the high speed relay passes F41 through its rest contact (pin 5) to the normal speed relay. Above 91 °C the temperature switch grounds the normal speed relay coil and the fan runs at normal speed.

Above 99 °C, or when the A/C pressure goes above 18 bar, the high speed relay coil is grounded. It switches F41 to the high speed winding and at the same time cuts the normal speed feed.

On 1994 cars the normal speed relay is also pulled in through pin 5 whenever the DME switches the A/C compressor (pin 48), so the fan runs while the A/C is on.

Check on your car

  • Drawn for a 1994 build. On 1993 and 1995 cars, normal speed relay pin 5 goes to the black/grey pressure-switch line (DME pin 85) instead of the compressor line.
  • Late 1995 cars swap the high speed relay pins: the blue fan wire moves to pin 5 and the green/red link to pin 2.
  • On 1993–95 six-cylinders with VANOS, high speed relay pin 9 also goes to the VANOS control module (pin 10, black/red). A non-VANOS M50 has no VANOS module; check that pin when swapping.

Redrawn from Bentley ELE-94, Engine Cooling 1993–95; diesel and M3 parts are left out.

1996–99: fan stage 2 relay K22

0.5 GN/VI fuse F16 5A fuse F41 30A 0.5 SW/GR pressure switch B9 / temp. switch S36 2.5 GN/RT stage 1 relay K21 pin 6 2.5 BL fan motor M9 pin 3 K22 Fan stage 2 relay fan stage 2 relay, X53 8 Coil supply (15) 6 Fan power 4 Coil ground (high speed) 5 Rest contact to stage 1 2 High speed feed

How it works

From 1996 the fan is run by relays K21 (stage 1) and K22 (stage 2). As on the earlier cars, stage 2 cuts the stage 1 feed when it pulls in.

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

1996–99: fan stage 1 relay K21

0.5 GN/VI fuse F16 5A 2.5 GN/RT stage 2 relay K22 pin 5 0.35 SW/GN temp. switch S36 X87 pin 3 0.5 SW/BR A/C line, splice X1022 2.5 SW/BL fan motor M9 pin 2 K21 Fan stage 1 relay fan stage 1 relay, X52 4 Coil supply (15) 6 Fan power 8 Coil ground (normal speed) 5 Coil ground with A/C 2 Normal speed feed

How it works

Six-cylinders switch stage 1 with the 91 °C contact of the dual temperature switch; four-cylinders let the DME switch it and only read the switch.

Redrawn from BMW ETM 6450.7 (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.