Light Bar Electrics

[Chimmychanga]

Hi
I have a 325i facelift saloon with check control and am looking at getting a lighting board for use with a bike rack. Does anyone know how this would wire in and if there are any pre prepared sockets for this anyware?

Any help would be appreciated.
Cheers

[Brianmoooore]

No pre prepared socket, I'm afraid. The 'standard' BMW trailer loom uses plugs that connect to the existing rear lamp clusters and sockets that connect as replacements to the clusters, with the trailer loom teed off between them. There might also be a version for cars with the lamp check module, although I've never come across one, but, if it exists, it should have a third plug and socket combo. that replaces the 'in' plug to the check module.
In the absence of this loom, you'll need to tap into the wires going into the module for the lamps that are subject to monitoring, and into the wires that bypass the module (somewhere between the module (near the aerial) and the rear right lamp cluster for those that aren't.
I have the wiring colours somewhere if you want them.

[Chimmychanga]

Thanks for the speedy reply as always - on a sunday night as well!
If you have the wiring colours that would be helpful. I guess that I could do without the check control panel working for when I was carrying bikes, In that case I would just have to tap into the light wiring in the boot.

Do you know how the monitoring module works? If it just checks for continuity then would it not still work if I just tapped into the lighting wiring?

thanks again

[Brianmoooore]

It's no more difficult to wire it in properly, that to do it incorrectly. The lamp check module is in the boot, on the LH side, almost touching the aerial.
'In' plug to check module:
Green/red (54) = brake lights = trailer red.
Grey/white (58R) = RH tail lamp = brown
Grey/yellow (58L) = LH tail lamp = black

Picked up from wires bypassing the module, or (easier) the loom from the module to the join to the LH lamp cluster:
Blue/black = RH indicator = grey (usually) indicator audio warning module = trailer green
Blue/red = LH indicator = orange = yellow
Grey/purple = fog = blue
Earth (stud under rear seat cushion) = trailer white

You can also dispense with the indicator audible warning module, and produce a more professional job by replacing the three pin indicator relay with a four pin one, with the fourth pin wired to a bulb fitted to trailer warning light position on the instrument cluster instead.

[Chimmychanga]

Thanks for the wiring -it works a treat. Now I just need to to the trailer warning light mod. Sorry for the stupid question but is the relay to replace the indicator relay by the steering column? I can't seem to find any info on the trailer warning light anywhere for some reason

[Brianmoooore]

The existing three pin 'relay' beneath the steering wheel is replaced by a four pin one intended for trailers. The socket for the 'relay' needs a terminal added for the fourth pin, which goes to the bulb that you fit to the instrument cluster. The other wire from the bulb goes to earth.

[Chimmychanga]

sorry to keep on with the questions. will that mean that the tow warning light will always flash regardless of whether the lighting board is plugged in or can it detect this somehow?

[Brianmoooore]

Trailer warning light will only flash when an indicator on the trailer is flashing. It's a legal requirement to have a visual or audible warning that trailer indicators are working.
Don't forget that towbars and towbar electrics sockets are now covered by the MOT test. A 13 pin socket is tested to ensure that it works, although the 7 pin version only gets a visual check of condition.

[Chimmychanga]

All fitted and done thanks again for the help. Only problem now is that the tow warning light seems to be alot dimmer than the others. Seems like the 4th relay pin only outputs 5v or something - but its hard to monitor it when its clicking on and off. I'm not too worried as it is bright enough to see its working though.

oh and while I had it out I found that the ABS lamp had blown so I replaced it. Now my ABS warning light is on YAY!

[Brianmoooore]

It's quite true that the trailer warning light is quite dim, but I've always thought that this was down to the green plastic being a bit more opaque that that used for the ordinary indicators. What does the warning bulb look like if operated out of its holder in the cluster? Can't say that I've ever considered the possibility of a lower operating voltage, although there's nothing in the 'relays' that would produce a lower voltage on the C2 output that I know of.
Start a new thread on your ABS light, and we'll soon sort that out.

[Chimmychanga]

The bulb outside of the holder looks dim too but like you I can't see any reason why the relay would output a lower voltage. When connecting it up to the standard indicator relay outputs it flashed brightly.

I'll have a look at the ABS light first and see if its anything obvious. Cheers