Using a Tail Light Converter for Toad Lights

mrschwarz · January 7, 2015

I just got a new Jeep as a toad. I am investigating using diodes and the factory tail lights instead of separate bulbs like I did with my previous toad. There are a few custom harnesses out there that connect directly into the factory wiring harness. I am using an Air Force One braking system. When the coach brakes are applied, the toad brakes apply and the toad brake lights illuminate. This can be a problem when one of the turn signals are blinking on the coach and I step on the brakes. As near as I can find, all of the custom wiring harnesses suffer from the same problem. When the brakes are applied in toad and the blinkers are on in the coach, the brake light will overide the turn signal. I contacted Blue Ox to ask about their unit and the technician on the phone confirmed that this would happen.

The are converters on the market that take the signals from a car with separate turn and brake lights and combine them for a trailer that only has a single light (combined turn and brake signal). With one of these converters, a constant on brake signal is interupted by the blinking turn signal. My thought is to connected the coach stop/turn lamps to the turn signal side and the toad turn/brake signal to the brake line side. This way, if the toad wants brake lights and the coach wants turn signals, the converter will let the coach's turn signals win.

Has anyone done this? Do I still need to use diodes? Is my reasoning faulty? Any opinions?

docj · January 7, 2015

I don't think what you describe is exactly the way things work, at least not for my MH and toad. My MH has combined brake light/turn signal bulbs which I think is what you're describing yours has. The electrical outputs from the MH through the trailer connector are for "left brake light/turn signal" and "right brake light/turn signal", not for "brake lights" vs "turn signals." Therefore, the bulbs in the toad will mimic exactly what the MH's lights are doing. When the MH is braking while a turn signal is on, the appropriate light will flash on and off while the other brake light stays on. The shop that wired my CR-V wired it so the brake lights flash to indicate turns rather than the amber bulbs that the CR-V uses for turns when we're driving.

What you're describing would be what the situation would be like if the MH had separate outputs for brake lights and turn signals; your's may, but mine does not.

I believe that the converters that you are describing would have made it possible to have the CR-V's light operate in a totally normal fashion, that is with the amber lights being used for turns. They must use the presence of simultaneous voltage on the two brake light bulbs to indicate braking even if one is flashing. That's how those "center brake light" add-ons used to work when those center lights were first introduced. However, I was unaware of such converters at the time my CR-V was wired and the shop either didn't know about them or didn't ask me. IMHO I don't think there's any problem with the way it is currently wired. Nothing affects how the lights work when we are driving.

Dutch_12078 · January 7, 2015

My coach and toad both have separate turn and brake lights. By adding one extra wire for the brake signal from the coach, and one extra diode for connecting to the toad's brake circuit, with the directionals wired normally on both ends, my toad and coach both have identical brake and directional lighting, complete with working high center brake lights on both. On my RAV4, I was able to tie into the appropriate wires behind the driver's side kick panel, saving having to route wires all the way to the rear of the car.

mrschwarz · January 7, 2015

Both vehicles use a single bulb on each side for brakes and turn signal. The problem is when the AFO applies the brakes on the toad and the MH wants the turn signals. The toad lamp gets constant voltage from the toads brake light circuit and blinking voltage from the MH. This results in the lamp being on constantly when it should be blinking, like the motor home.

If you took an auto that had separate turn signal and brake lamps, connected them to a single lamp on the back of a trailer, the same situation would exist. You would have a blinking voltage and a constant voltage going to the lamp at the same time. The converter is designed to interupt the constant voltage from the brake light circuit when the turn signal wants the lamp to blink.

My thought is that if the single brake/turn wire from the MH was connected to the turn signal input of trhe converter and the toad's single brake turn lamp was connected to the brake light input of the converter, the toad's brake light voltage would be interupted when the MH's turn signal was supplying blinking voltage. When the toad is disconnected from the MH, there would never be a voltage on the turn signal side of the converter and the tail light would either be on or blink based on the toad's requirements.

Since the converters are relatively inexpensive, I am going pick one up and play with it. The converter has to have some form of isolation to keep the inputs from being combined, but I will probably put diodes everywhere since they won't hurt anything and it better to be safe than sorry.

I'll report back to let you know if it worked.

Dutch_12078 · January 8, 2015

A couple of small 12-volt relays would solve the problem. Connect the coils to the line from the coach for each side, and the normally closed contacts so they interrupt the toad brake signal for the appropriate light when the coach directional is active for that side. The coach and toad directionals will be out of sync, but I don't think that matters. The brake lights of course, would still operate normally as far as following traffic is concerned.