Tow bar electrics

[mr self destruct]

I've recently fitted a tow bar to my gti, managed to wire it up with no difficulty at all as there are a load of little tabs on the light clusters. Question is, is this what they're really there for?


They're connected to each light like so:


Now all the lights, while they are getting current, are quite dim. This is especially noticeable on the indicators. They run fine when the light board's not connected, but are slow and dim when it is. Its definitely a problem with the car, as its the same if I use my light board, trailer, or trailer tent.
Could it be because the same amount of current has to go through an extra bulb plus a few more feet of wiring?
Or is it because I used a thicker gauge of wire than on the loom when wiring up the tow bar?

Any ideas?

[Wayne]

Are you running it through a relay.

[mr self destruct]

No I'm not. Is it needed on a car this old?
If so, how do you wire one of those in (do you have a diagram?), and do all the lights need them or just the indicators?

[Ben Lessani]

I would have thought because the indicator relay is driven off resistance that you'd need to add a relay in for a tow bar repeater, otherwise, like you've noticed, it will slow down.

But none of the lights should be particularly dim, unless you've wired them in series - not parallel.

[Wayne]

As above, you need a relay to be honest.

[monzablue16v]

Have you got a good earth? measure the voltage at the cluster and then again at the trailer board, process of elimination really, indicators will need relays others should be ok saying that I think you can get towbar relays with many input and outputs all driven from a good power feed.

[rubjonny]

that is exactly what those tabs are for, that and 3rd brake lights n stuff
you will need another relay for the indicators as said, etka lists different ones for trailor towing

[mr self destruct]

Cheers for the replies guys, I'll definitely get a relay in then.

rubjonny, by that do you mean I'll need a diferent spec relay to replace the original one, or wire another one in as well as that?

And if so, does anyone have a diagram or sketch showing how to wire in an extra relay?

[rubjonny]

you swap the std relay for a different one, etka lists it as:
431 953 231 - turn signal/hazard light relay, for models with towing facility - 26.22+VAT

check zee fusebox faq for the relay location, but its the one with '21' on it

[mr self destruct]

Cheers for that mate, I had to plot my route home from Big bang this afternoon with as few right-turns as possible - especially with a copper behind me all through Northampton!