Off load Circuit functioning

[RB2]

I have an intermittent problem which seems to be something to do with the off load circuit.

When I have the problem the following doesn't work.

-heater fan
-Danthe circuit cooling fan (fuse3)
-electric mirrors
- brake pad warning light.

These all work prior to starting the car (2 clicks of the keys lights on the dash), the Windows will work if either door is open whilst the car is running.

If they don't work if I stop and start the car a few times it will end up working.

Sometime just driving for a few miles will get them started.

Once they start once they will continue to work until the ignition is turned off.

I've replaced earths, even fitted jump leads as additional earths with no joy.

I've been swapping relays from my M Coupe with no joy.

Best I can see is its related to the offload circuit which is why they work prior to the engine running.

Does anyone have any info on the off load circuit and its function/wiring/component location.

All ground points have less than 1 ohm to the neg terminal.

Any help would be super as it's being a nightmare to pin point.

Thanks very much.

[RB2]

Back ground to the car

It's recently had an m52 swap by myself.

loom X-over
fan loom
Mishimoto pusher fan
ECU Map
6pot dash code chip

I've also Coverted it to manual so the centre console wiring was changed to suit.

The rest of the electrics are oem. I have pulled the fuses for the cooling stuff to see if that would help but it makes no difference.

I am 99% everything was fine prior to fitting the M50 inlet. I've checked the loom over the bulkhead incase anything there got a bash but it all looks good. So this is maybe just coincidence

I am in doubt it's a partial broken wire etc due to once it starts to work it doesn't stop

[Brianmoooore]

Heater fan, correctly wired electric rad. fan and mirrors are all associated with unloader relay K7, but the brake pad warning light is not.
The windows, with the doors shut, are associated with unloader relay K5.
The common factor between the two unloader relays is the black/green wire to the starter motor.
There is, however, a common factor between the heater fan, elecric rad.fan, the mirrors and the pad warning light, and that's fuse 10. Fuse 10 is also for the reverse lights, so check if they work while the car is acting up.
So, five faults, with one common factor between four of them, and another common factor between a different four of them.
Check that fuse 17 hasn't blown, which would but the windows out of action with the doors closed, so eliminating K% from the suspect group if it was.
Temporarily remove relay K7 and link together pins 30 and 87 of its socket with a piece of wire for a while, and see if that 'cures' some of the problems.

[RB2]

Fuse 17 = 0.5 ohms
K7 relay pin 30 to 87 linked. Cooling and heating fan active. Brake pad indicator illuminated.
Still red to check the reverse lights.

When I talk of the brake pad indicator, the light will be on on the dash and the second the fans kick in the brake pad indicator goes out.

Just away to rig up a mirror to see if the reverse lights are working.

[RB2]

So I maybe have two problems

The reverse lights are not working but I've just managed to get the brake light on on the dash with the cooling and heating fan working.

[RB2]

30 to 87 linked = fans, Windows and mirrors working but the brake indicator (illuminated) and reverse lights don't work.

[RB2]

What energises 86 to 85 on k7 then?

I am pretty sure it's not the relay as I've been swapping them about with relays from my other BMW.

[Brianmoooore]

F10 provides the power to energise relay K7 (the supply to K5 is unfused, direct from the ignition switch). Check out F10 by swapping it with another 7.5A fuse, if not obviously blown.
If it is blown, then the wiring under the car to the reverse light switch is the likely culprit.