Late model BX aircon wiring

[tomsheppard]

NB Webmaster. I've submitted this for inclusion in the hints and tips column should you approve.
Late cars differ from early cars and the engine fans are switched in the positive line and not to earth like early cars.
Circuit diagrams being non-existent for this system, it has been necessary to invent it.
Two cars have so far been wired to this pattern with success.
Two four pin relays are needed. Relay 1 controls the engine fans and relay 2 works the aircon clutch.
Take a stout wire from the black connector beneath the battery to a 20 Amp fuse.
The other side of the fuse runs to:
Pin3 of relay 1 and
Pin3 of relay 2.
Pin5 of relay 1 connects to the fan low speed contact of the fan switch at the fan itself.
Pin5 of relay 2 connects to the clutch on the compressor.
A wire runs from the aircon controller (60). It is a grey wire with a yellow connector which becomes live when the a/c is switched on.
From this wire, run a wire through the bulkhead and connect this to: pin1 of relay 1 and
pin 1 on relay 2 and
to pressure switch pin 3(white).
Pressure switch pin 4 (black)splices into:
the green wire joining relay(772) pin2 and relay(773)pin 2.
Relay 1 pin 2 runs to earth.
Relay 2 pin 2 runs to pressure switch pin 1(blue).
Pressure switch pin 2 (green) goes to earth.
Testing:
Switch ignition to position 1, switch on aircon.
Fans run slowly.
Clutch remains out until there is pressure in the system so if you are not yet gassed up, short pressure switch pins 1 and 2 and the
clutch comes in.
short pressure switch pins 3 and 4.
Fans now run fast.
Switch off aircon. Clutch drops out and fans stop.
That's it.