tow bar

Welcome to the forum.

I fitted a 13 pin trailer plug to my E60 myself using the 13 core wire.  I used a bypass relay for the trailer lights (black socket) and a split charge relay for the internal lights (white socket)

The 13 pin socket shound have the following if wired correctly

pin #1 LH indicator Yellow 
pin #2 Fog Blue
pin #3 Earth for pins 1 -8 White
pin #4 RH Indicator Green
pin #5 RH Tail light Brown
pin #6 Brake lights Red
pin #7 LH tail lights Black
pin #8 reversing light Pink
pin #9 Car 12V fixed supply Orange
pin #10 Fridge switched supply Grey
pin #11 Earth for pin #10 White/Black
pin #12 No allocation (spare) White/Blue
pin #13 Earth for pin #9 White/Red

If wired not quite so well it could have been wired with two 7 core cables, a black one for the trailer lights and a grey cable for the internal lights.  If the socket has been wired with two 7 core cables it can be tricky to get a good seal around the cables on the back of the socket housing.  Water may have got into to the socket and is creating a problem. 

I take it that you just bought the car which has already had the towbar and electrics fitted?

It sounds like someone hasn't wired the car up correctly when fitting the towbar wiring.  Or it has chaffed and it shorting.  Or your adapter may be at fault?

Don't use it if it makes the autobox fault.  The last thing you want to do is make your autobox fall over.  Get the wiring checked out in the back of the car.  As the white socket supplys the trailer reverse lights which ais controlled by the autobox (the trailer reverse lights are earthed thru the black socket) this could have a short which is then upsetting the autobox.

Towbar wiring is straight forward but you may need to strip out all the trim panels in your boot to see it and remove the bumper too.

HTH

Andrew

PS, please don't use caps.

If you have replaced the socket with a new one, I would guess that the problem then lies at the other end of the cable, in your boot.

I'm not suprised the wire colours are different.  Manufacturers will make their own wire colours up, just to be different or awkward or to match wire colours in the boot.

I would re-wire the cable in your boot.  You will need a split charge relay and possibly a bypass relay.  The BMW towbar loom will/should have a split charge and bypass relay built in to it, but I suspect this loom is faulty so you could replace it with one you can make your self using the existing cabling and 7 core towing cable which you can get from Halfrauds or 13 core cable which you should get from a caravan accessory shop.

Pin #9 red/blue, this should be wired to a permanent 12v supply in your boot.  Ideally direct to the battery + post with a 15 amp (or is it 30 amp?? )fuse in line.  I connected my pin #9 directly to the back of my fuse box in my boot.  Taking the rear cover off exposes a couple of 100 amp fuses which have a nut and bolt connection, undo the nut and pop a ring connector on.

Pin #10 blue should be wired to the switched output of the split charge relay.  This pin serves to supply the fridge but only when your ignition is switched on i.e. your engine is running so you aren't draining your car battery  The spilt charge relay can be bought from Halfrauds for £30, £20 if you search the internet for a different supplier.

Pin #11 should be connected as this is the earth for your pin # 10 without this conencted your fridge won't be on when you are driving.  See pin #13

Pin #12 doesn't need to be connected so you are o.k.

Pin #13 brown should be connected to earth.  This can be any bolted conenction on to the body work.  There is bound to be a few suitable points around either light cluster.  Or a bumper securing nut/bolt.

Pin #8 green/yellow wire needs to go to the reverse light supply ideally via a bypass relay.

Pins #1 -7 and #8 should be conencted to a bypass relay.

A bypass relay should be installed to protect your cars lighting circuit from overload and to prevent onerous fault messages displaying on your dash.

The lights in your BMW flash. They are not on all the time but flash faster than the naked eye can detect but to you and me they appear on.  The ECU sends pulses of power thru the wires to the bulbs.  This means BMW can fit thinner wiring and save 2p of copper on each car which adds up when you make a few cars a year.  When you add additional lights, i.e. when towing a trailer to these 'pulsing' systems it can upset the cars electrical system.  

To get round the BMW's wiring system you need to fit a bypass relay.  It works by receiving a signal from the wire that supplies each rear light.  Once a signal is received it then switches on a 12V supply from the battery which then sends the power down the cable to the socket and then into your trailer lights. 

The bypass relay only draws a few milliamps more from the cars circuits so the car does not detect the extra load as this will be within tolerances.  A 21W bulb from one manufacturer will draw more current that a 21W bulb from another, so there has to be 'give' in the system. Using a bypass relay means the cars bulb failure system is unafected by the trailer lights.

The bypass relay connects to the cars wiring system at each rear light cluster.  You tap into each relevant wire using a red piggy back connector (Halfrauds) one at a time and take a wire back to the bypas relay which is mounted in the boot.  The bypass relay requires a fused 12v feed.  I took this from the back of the fuse box which is mounted in the boot of my E60 just above the battery.  You then connect the cable to the socket, pass thru the boot floor using a rubber gromit and then wire the cable into the relevant connection on the bypass relay.

I got my towbar and bypass relay from these guys £10 for next day delivery I think.

http://www.towbarsdirect.co.uk/

and I spent a bit of time reading this guys website.

http://www.rydertowing.co.uk/default.htm

Also have a read of this

http://www.rydertowing.co.uk/downloads/pdf_checklists/Practi cal%20Guide.pdf

I hope this helps, but feel free to ask more questions.

Andrew

No problem Roger.

Stay around on here, you can learn alot about your car if you are into that sort of thing.

It would be good to hear from you once it's sorted.

Glad I could be of help.

Andrew

By using a bypass relay you avoid the possible upsetting to the BMW CAN bus wiring.  Where did you read not to use one?

The relay take a 12V fused supply from the battery so no weird signals in that wiring unlike the CAN Bus.  The relay takes a signal from each light in turn which then triggers the relay to switch the 12v straight from the battery to that particular trailer light.  The bypass relay keeps the trailer lights/supply voltage completely seperate from the car loom/the CAN bus etc so it doesn't upset the car system.  This also means if a trailer bulb fails you do not get any warning on your dash.

My PDC is not disabled when I hitch up.  I just simply switch it off on the dash.  If I had parted with £180 for the BMW towabr wiring loom then paid BMW to code the electrics to my car then the PDC would switch off automatically on connecting the trailer plug to your car socket.  The BMW towbar wiring loom would detect the trailer electrical load and switch off the PDC.  The BMW towbar wiring would also fire a warning on the dash if a trailer bulb failed.

I bought a detachable towbar as I thought a fixed one would interfere with the PDC, but when my towbar is in place the PDC cannot detect it anyway!

I have had no issues with my home made towbar wiring in the nearly 3 years it's been fitted.  I was towing on Friday with no issues.

Let me know if you need anymore help.

Andrew

Interesting point regarding the German MOT thing.  The bypass relay makes an audiable buzz when the trailer indicaters operate.  No noise means you have a blown trailer indicater bulb.  But I have no way of knowing a trailer tail bulb is out.  Plus my bypass relay is buried away in the boot floor so I can't actually hear it from the drivers seat but I can hear it if I stand outside.]

The towbar will form part of the MOT test in the future but I don't know if that includes electrics to cover for a failed bulb etc. 

If you are worried about towing weights and you have the option of buying another car, the E60 can tow 2000kg and has a nose weight limit of 90kg.  A Ford Mondeo, previous model, can also tow 2000kg, can't recal what the Mondeo's nose limit is, it would be atleast 75kg. As modern cars get heavier with all their associated safety gubbins their allowable towing weights increase.  A Ford Sierra from the late 1980's would be good for about 1500kg max.  It's much younger brother the Mondeo weighs a lot more with all its roll cages, air bags safety cells, crumple zones etc etc so it has the mass to assit in towing.

Overloading the car in terms of max towing weights is unsafe for you, your passengers and any other road users around you and probably invalidates any insurance claim you may make if an incident occurs while towing.

That will be OEM so it should fit like a glove and be totally unobtrusive once removed.  You can't see my Westfalia unless you are right underneath looking up behind the bumper.

Let me know how you get on fitting it.

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