Quick question guys since yous have all been so helpful. When wiring up a tow bar, do I actually need a bypass relay? I don't think the car has a bulb detection system so I don't see a real need to have one but I'm sure someone here will be certain

Hi, 

I fitted a tow bar to mine last week. I don't have bulb failure detection so I went for the normal buzzer type relay. Every works as it should. 

Peter. 

May be worth considering the extra (almost doubled) current through the brake light switch, already a common failure in mature Fabias, before ruling out the idea. 

Just now, Wino said:

May be worth considering the extra (almost doubled) current through the brake light switch, already a common failure in mature Fabias, before ruling out the idea. 

Hi,

I didn't think of that, I went for the easy option to avoid running a cable the full length of the car. 

I'll probably swap it now as I could do with a 12volt socket in the back so will do both together. 

Peter. 

I personally have always wired up my towbar in the quick way using either connector blocks or scotch locks to the back lights, I get that this will draw extra current through the wire however the bulbs on my caravan are all 3w bulbs, so 6w (1x bulb each side, 2x3w=6w) at 12v = 0.5 amps... so it will only be half an Amp or an increase, chances are the cable will be able to hold it without melting, any other reason this is not a good idea?

 

If Im honest it seams a very simple setup and I wonder why people would buy these bypass systems but I imagine someone will know why its not best to just do it the way I have.

Never heard of 3W brake light bulbs, but even so, the steady state current isn't what's relevant for the brake light switch contacts.  The cold resistance of bulb filaments is a tiny fraction of the hot resistance, so the current surge that the switch has to deal with as its contacts close every time you brake is waaay higher. 

Ahh right. I didnt take temperature into account, never thought about that, Correct me if I am wrong but as long as the fuse does not blow when I test it, then in theory it should be a low enough current to be all good?

The wiring will be fine, but the brake light switch will have a shortened life-span.  Not a big deal, because you should get a warning EPC light on the dash when the switch fails, so you shouldn't be running around not realising your brake lights aren't working.

I dont think mine has an EPC light (Noticed some of the dash lights have faded/disappearing but all of the essential ones still there lol)...

 

I check my brake lights often so in theory my setup should be "good enough"?.... Where's the brake light switch located? Back of the brake or are we taking about a relay switch or am I miles away?

 

Im just thinking wether or not its worth my time to wire it up "Properly" to avoid burning out the brake switch

Sorry, yours is diesel, it'll be the glow plug light that warns you then.  Yeah, 'good enough' I'd say, especially if your brake light bulbs on the caravan really are that teeny.

Brake light switch is activated by the pedal, up under the dash trim.

Never heard of a 3 watt brake light bulb. Surely that's not right?

Perfect mate thanks very much, yeah the bulbs really are as low as that.... the fact your are saying that no brake light as as low as 3w kinda concerns me as to wether mine are legal or not lol. They're not super bright but I presumed they were bright enough as it had been being towed regularly.

 

Just on the off chance, any idea what brake lights wattage ussually is? and whether its legal to have 3w bulbs? If you dont know dont worry man, you've more than helped enough. Im sure PC Plod will be happy to tell me whether they are legal or not at the roadside one day lol.

 

 

Filament brake bulbs are normally 21 Watts.