Towbar wiring (properly) - BMW e39

[BenzBoy]

I'm fitting a towbar to the BMW e39 touring. The one I've bought comes with a towing interface, however I don't really know the best way to wire it in. The instructions are generic and don't give specific vehicle info.
Is there some sort of plug on the e39 loom to plug in a towing interface (even an OE one)? Or do I have to somehow splice each wire that goes to the lights (seems like bodgery to me!).
The e39 has a Light Control Module so the circuits aren't fused in the regular way, and this LCM can get fussy and bring up bulb failure warnings if things are messed about with.
Every thread I've found on the internet seems to end with "take it to a towbar installer".
Any help much appreciated!

[healeyneil]

Pre facelift doesn't have any plug - at least mine didn't. I hade to splice -by soldering. The worst to reach was the fog light I think.one in the tailgate. I reached the feed for that behind the roof speaker. Not a difficult job. Just a faff.
Neil

[mashedpot8er]

Hi There. I've got all the stuff that I took out of my 98 E39 saloon that the previous owner put in, if you want it. It was a couple of white boxes, bit longer than a fag packet and a load of wires. I'll grab a photo for you. BRB.

Here ya go. It was all spliced into the offside tail light wires. I can't help you with installing it, but if you want it pm me and you can have it for nowt.

[carat 3.6]

Feb 7, 2018 10:20:30 GMT BenzBoy said:

I'm fitting a towbar to the BMW e39 touring. The one I've bought comes with a towing interface, however I don't really know the best way to wire it in. The instructions are generic and don't give specific vehicle info.
Is there some sort of plug on the e39 loom to plug in a towing interface (even an OE one)? Or do I have to somehow splice each wire that goes to the lights (seems like bodgery to me!).
The e39 has a Light Control Module so the circuits aren't fused in the regular way, and this LCM can get fussy and bring up bulb failure warnings if things are messed about with.
Every thread I've found on the internet seems to end with "take it to a towbar installer".
Any help much appreciated!

I'm guessing by "towing interface" you mean bypass relay? These are very easy to wire up, just a fused live and earth from the battery, and a feed from each light. They don't draw power from the lighting circuits so the lcm will be happy.

[discostew38]

Fitted mine recently
No big deal the worst job is getting to the live wires for the fog and reverse lights
I only fitted a 7 pin plug so didn't need the reverse light
but as I had to chase the loom for the fog light wire I didn't matter if I planned ahead
So if you want trailer only you need a bypass relay (this stops the dash warning lights)
And if you want caravan plug as well you need a split charge relay

All the relay kits come with scotch locks
But I don't use them I solder all the wires into the loom

[bmw2101]

i have a detatch witter i got from work and a ryder relay.

Now, where does the loom pass to the tail gate? I need to get a feed into the relay for the reverse lights on my car, ive used the replay to power my after market chinese reversing sensors, but cant find a feed.


thanks

[discostew38]

Feb 7, 2018 21:56:18 GMT bmw2101 said:

i have a detatch witter i got from work and a ryder relay.

Now, where does the loom pass to the tail gate? I need to get a feed into the relay for the reverse lights on my car, ive used the replay to power my after market chinese reversing sensors, but cant find a feed.


thanks

If it's a touring the tailgate loom runs up the "C" post on the o/s 

[bmw2101]

yes it is, thanks, ill have a look.

[BenzBoy]

Feb 7, 2018 19:18:59 GMT healeyneil said:

Pre facelift doesn't have any plug - at least mine didn't. I hade to splice -by soldering. The worst to reach was the fog light I think.one in the tailgate. I reached the feed for that behind the roof speaker. Not a difficult job. Just a faff.
Neil

Ah, I've had the joy of fitting a replacement tailgate so I know the joy that is the million wires running up in the roof. I never found a wiring diagram for the tailgate to work out what wire does what.

Feb 7, 2018 21:43:28 GMT discostew38 said:

Fitted mine recently
No big deal the worst job is getting to the live wires for the fog and reverse lights
I only fitted a 7 pin plug so didn't need the reverse light
but as I had to chase the loom for the fog light wire I didn't matter if I planned ahead
So if you want trailer only you need a bypass relay (this stops the dash warning lights)
And if you want caravan plug as well you need a split charge relay

All the relay kits come with scotch locks
But I don't use them I solder all the wires into the loom

I'll be sure to solder rather than use scotch locks, and it's only a 7-pin plug I'm using so reducing the wiring headache will be welcome! More wiring through the speaker holes... hurray!

Feb 7, 2018 19:39:13 GMT mashedpot8er said:

Hi There. I've got all the stuff that I took out of my 98 E39 saloon that the previous owner put in, if you want it. It was a couple of white boxes, bit longer than a fag packet and a load of wires. I'll grab a photo for you. BRB.

Here ya go. It was all spliced into the offside tail light wires. I can't help you with installing it, but if you want it pm me and you can have it for nowt. ]

That's very kind of you! I've got a box with the towbar so should be OK, but thank you for the offer.

Feb 7, 2018 20:12:42 GMT carat 3.6 said:

Feb 7, 2018 10:20:30 GMT BenzBoy said:

I'm fitting a towbar to the BMW e39 touring. The one I've bought comes with a towing interface, however I don't really know the best way to wire it in. The instructions are generic and don't give specific vehicle info.
Is there some sort of plug on the e39 loom to plug in a towing interface (even an OE one)? Or do I have to somehow splice each wire that goes to the lights (seems like bodgery to me!).
The e39 has a Light Control Module so the circuits aren't fused in the regular way, and this LCM can get fussy and bring up bulb failure warnings if things are messed about with.
Every thread I've found on the internet seems to end with "take it to a towbar installer".
Any help much appreciated!

I'm guessing by "towing interface" you mean bypass relay? These are very easy to wire up, just a fused live and earth from the battery, and a feed from each light. They don't draw power from the lighting circuits so the lcm will be happy.

Yeah I guess it's a bypass relay, I'm just going off what it says on the box. Load of wires going in, and a load of wires coming out. Perhaps I'm thinking this is a more complicated job than it is!

Thanks for the replies everyone

[pow]

I've used one of those towing relays in my pre-facelift e39, no issues witht he LCM or any errors on the dash, works perfectly I don't have parking sensors so I used the parking sensor grommet to pass the wire out and then to the towbar. I picked up the live from a spare fusebox live above the battery and bolted the relay gubbins next to the battery.

[bmw2101]

just on the parking sensors again, the bmw ones never worked, i bought all new chineese ones, didnt work, got second hand ones, still didnt work, cost a fortune. So i bought a cheep chineese kit of ebay for £20, fitted teh sensors in the original bumper holes, and when i can sort the reversing live to the ryder relay I'm sure itll be mint.

[discostew38]

I had the same problem
The parking sensors on My previous e39 didn't work and I spent ages tying to sort them out and never did fix it
And when I bought this one it was the same I couldn't be bothered to find out why I just fitted a new Toyota kit I had laying about




Bit of aerosol and as good as new

[surprisingskoda]

IIRC around the nearside rear light on a touring I took a genuine bar off, there was a black 8-pin plug that was wired into the light circuit, and one thin brown wire that ran all the way to the LKM in the drivers footwell.

Probably no help, unless that plug is there.

[ChasR]

Feb 8, 2018 17:30:27 GMT bmw2101 said:

just on the parking sensors again, the bmw ones never worked, i bought all new chineese ones, didnt work, got second hand ones, still didnt work, cost a fortune. So i bought a cheep chineese kit of ebay for £20, fitted teh sensors in the original bumper holes, and when i can sort the reversing live to the ryder relay I'm sure itll be mint.

The Chinese sensors as you have found out for the BMWs are rubbish. One way around them is to get the copies fitted to the middle of the bumper but even that comes with its compromises. My friend's E46's two in the middle see stuff around all of the time. When I hooked up INPA we were able to see this as it gives you live data off the sensors, which can be very helpful for diagnosing the stock sensors and save quite a bit of time.

The aftermarket kits can be variable and some of them do look cheap IMHO in comparison to a stock sensor and have very slow response times. But some aren't too bad. The Amazon kit I fitted to my sister's car looks almost OE and is very responsive. I can't say the same about the Maplin kit on the Mondeo we sold it ; The display was more informative than the beeps which were quite confusing.

At the price of the kit we got from Amazon it's a great way for even tight people to save damaging their rear end. Stop sniggering now!

[BenzBoy]

I'll investigate on the plug surprisingskoda, thanks. That would be a nice easy solution.

My e39 is an earlyish one with no parking sensors so I don't have that to worry about. It does have SLS air suspension but I'm guessing that it just sorts itself out without needing to know there's a trailer attached.

[discostew38]

Feb 9, 2018 10:55:46 GMT BenzBoy said:

I'll investigate on the plug surprisingskoda , thanks. That would be a nice easy solution.

My e39 is an earlyish one with no parking sensors so I don't have that to worry about. It does have SLS air suspension but I'm guessing that it just sorts itself out without needing to know there's a trailer attached.

Yeah the suspension work off the hight sensors so it will sort its self out 

[ndg]

The OEM towing module has a wire to the LCM. When the car is connected to a trailer the LCM disables the rear PDC and foglight. I quoted my E46 up this way and it works well.