Towbar electrics

[stulemanski]

I've fitted a towbar to my Superb. But not the electrics...

 

Frustratingly, my car wasn't towbar prepped and the Westfalia kit that came with it is missing the loom that runs from the Westfalia towbar module to the BCM module at the front of the car. Westfalia don't sell just this loom, but it looks like I could get the correct part from skoda-parts (3V0 055 204 C) for about £60. I would then have to pull off all the interior trim down one side of the car, run this loom from front to back, and then get the computer recoded once it's all connected up.

 

Alternatively, I could just get a bypass relay to run the 7 pin socket for about £25, which would cut into the loom by the tail lights. No recoding necessary, and I don't have to pull half the interior out. 

 

Westfalia have claimed that a bypass relay isn't appropriate for my vehicle (but have kindly offered to sell me a whole new towbar electrics kit for £170), but an auto electrician has told me that a bypass relay is okay (he won't fit my secondhand Westfalia towbar module but will fit a bypass relay that he'll sell me...) Obviously neither opinion is entirely unbiased, so I'm coming to the collective wisdom here for advice...

 

Assuming there's no technical reason why a bypass kit wouldn't work, I'm wondering whether the fancy kit is worth it, as (1) I don't have parking sensors, so don't need them turned off when I put the car in reverse, and (2) I'm only going to be attaching a bike rack (not a caravan) so don't need the stability program to act as if it's towing a trailer when the 7 pin lightboard is connected. 

 

So, is there any good reason for me to go for the whole module instead of just a bypass relay?

 

Thanks in advance!

[SashaGrace]

Bypass really is a bad idea IMO, get the proper loom, code the car and have the ACC radar recalibrated correctly. The car needs to be told it has the bar on it as there are 7-8 modules that need telling about the bar.

[stulemanski]

I don't have ACC either...

[J.R.]

There is absolutely no valid reason for you to go to the time, cost and expense for your use.

 

The modern high impedance towing relays work faultlessly but are only as good as the butcher who connects them to your existing wiring.

 

I have fitted many over the years and the modern ones incorrectly described as Canbus compatible are far better than the old ones where you had to push coils of wire around a core to get the audible warning to work.

 

The only downside, and its a tiny one, is that the relay draws power 24/7 and will reduce the autonomy of your vehicle battery if you go on a months holiday, they are a lot better than they used to be and many vehicles have a really high parasitic consumption anyway so their effect is minimal.

 

Mine has a low standby consumption and the relay increases it by 30% meaning the autonomy on my larger battery would fall from 6 weeks to a month (all guesstimated figures from memory) I have a switch in the boot to only turn it on when its needed, on the previous vehicle I just removed the fuse.

[langers2k]

8 hours ago, J.R. said:

The only downside, and its a tiny one, is that the relay draws power 24/7 and will reduce the autonomy of your vehicle battery if you go on a months holiday, they are a lot better than they used to be and many vehicles have a really high parasitic consumption anyway so their effect is minimal.

 

Surely you can just connect it to an appropriately fused, switched ignition live and the problem is solved...?

[Breezy_Pete]

I think the rationale for the permanent feed is so that hazard lights will work on the trailer board even with ignition off; though that's only a guess.

 

[J.R.]

That was my initial thought Langers after inheriting a module professionally fitted (= butchered wiring) on an Octavia but I thought of two reasons why it had been done that way, the hazard flashers as Wino mentioned and also side/parking lights.

 

I could see a breakdown situation where the choice would be either unsafe and a danger to oncoming traffic or safe but insecure with the keys in the ignition.

 

Actually the professional wont have been using any logic as it was hardwired unfused direct to the battery terminal , that one had a significant current draw, the ones I have used since then much less so.

Edited 23 July, 2021 by J.R.