Toad/Towed Wiring?

where2

Veteran Member
Joined
Oct 29, 1999
Location
North Palm Beach, FL, USA
TDI
One '13 JSW_TDI & One '04 Variant_TDI
I'm an OCD wiring person, and I have questions for anyone who has wired their own VW as Toad/Towed vehicle. Having recently acquired a class A RV, with all the other accessories it needs to bring along a Toad/Towed (dinghy), I've been thinking about how to drag my MkIV Wagon behind the RV as the dinghy. (the accessories I got were previously rigged for towing a GMC Traverse, but I'm not keeping the Traverse...).

My first question is about brake lights: Most toad/towed wiring kits intend to use the turn signals as brake lights and turn signals. However, most states require a toad to be running an auxiliary braking system (electro-mechanical foot on the car's brake pedal). I've got an RVi3 braking system, if it is doing it's job, aren't the brake lights on the vehicle going to illuminate automatically while the Toad/Towed vehicle is braking, courtesy of the aux braking system depressing the brake pedal?

My second question is about license plate lights: How is it that no Toad/Towed kits seem to address license plate light wiring? I've been the lucky recipient of a "Fix It" ticket for driving said MkIV with one of the two license plate bulbs burned out. How does the RV world get away towing cars without illuminating the license plate on the dinghy? Does everyone pull over to turn on the parking lights on the Toad/Towed when the sun goes down, or when it starts raining? The toad/towed typical wiring kit will power up the tail lights off the brown wire from the typical trailer wiring connector. That doesn't light the license plate lights on a VW though.

Anyone with a Toad/Towed running a battery charging system? Obviously, the auxiliary braking system takes power to operate running down the road. If the brake lights are operating due to the aux braking system, then that's more energy I'll need to replenish. Is there any advantage running the "typical" battery maintaining/charging system, versus running an intelligent battery combiner system? The combiner would parallel the 12V on the trailer connector to the Toad/Towed vehicle battery when the RV trailer connector is supplying greater than 12.7V DC. Assuming I'm getting 12.7V or greater out of the trailer wiring plug, why should I step through the typical isolation diodes (-0.7V) when a combiner would work fine and offer a greater potential charging voltage.
 

bobbiemartin

Veteran Member
Joined
Jul 16, 2012
Location
Jacksonville, FL
TDI
2010 Tiguan TDI 4Motion, Jeep Grand Cherokee 3.0 CRD
If you are looking for an additional rear light, there is an unused spot in the taillights for rear fog lights. This takes a single filament bulb which could be wired as turn/stop lights when towing. I would think you could tap into the parking light circuit for running lights. I don't know why the license plate light would be on a different circuit, but if so you could run them through a relay and have them operate normally when driving and light up with the parking lights when towing. As far as the brake lights working with your braking system, as I recall the brake lights only work with the ignition on, so they would not work unless you leave the key on.
 

SilverGhost

Veteran Member
Joined
Mar 25, 2005
Location
Back in So Flo - St Lucie
TDI
'05 Golf - totaled :(, wife's '13 Beetle - buy back, TDIless
Ask the Germans - because (I think) they have the ability to turn on park lights on only one side at a time, and don't need lic for this, is why the lic plate lights don't come on with park lights. German (and assumed other EU states) require park lights on parked car on certain narrow streets. No need to completely rewire the car to pass US DOT.

BTW a couple wires between the turn signal switch and ignition switch on your car will make this function work.

You can tap into lighting at the light switch pretty easily. A diode tree should allow you to turn on tail and lic lights without the car getting screwy. Its 58L and 58R for the tail lamps, 58 for the lic lamps. Then a bulb in rear fog position and run that for stop/turn.

Jason
 
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