Trailer Electrical Wires

[daviddoria]

I bought a 30 year old trailer to haul a boat. However, all the wires were all corroded. So i ran all new wires. However, when i step on the brakes and have the lights on, the right light is off and the left one lights up. every other function works fine (ie, left turn signal with and without lights and brakes and so forth)

any idea what could be causing this?

thanks

david

 

[Russlk]

10 to 1, the right light that goes off has a corroded ground. The extra current of the brake light heats the corrosion and opens the ground, a common problem. Try cleaning the connection, or put in a new bolt.

 

[daviddoria]

excellent, i'll try it tomorow and let you know. sounds very possible as it is all rusty.

in the mean time.... i dont really understand how it works....

if you have 2 voltage sources together, isn't that not good? for example, if there are 2 wires running to one side of a light and the other side is grounded, is that ok? cause that seems to be what is happening here when the breaks are hit while the lights are on... 2x 12v is going to the light. that should make it 24v and be twice as bright, correct?

thanks

 

[gerty]

I'll bet Russ is right, as far as the 24volt question it's not 12x2 it's the same 12 volts,after all you only have one 12 battery . The bulb should have 2 filaments, one for tail light,one for brake/turn signal and is the brighter of the two. Also make sure you have a good ground to your tow vehicle, another common problem.

 

[ChrisP]

BTW -- Just a point of interest for those out there using older trailers with newer towing vehicles...

Most boat/utility trailers use four wires:

• right turn;
• left turn;
• tail; and
• ground.

The stop light tie-in occurs in the towing vehicle's turn signal/hazard switch. One of the problems that occurs with many newer (towing) vehicles is that there are stop lights that are separate from the turn signal lights.

Most older vehicles used a single dual-filament lamp for the functions of tail light, stop light, and turn signals. The lower candlepower filament was used for the tail light function, while the brighter filament was used for both turn signal and stop light/hazard functions. Thus, if the driver applied the brakes with the turn signals "off", the current from the stop light switch was routed through the turn signal/hazard switch to both rear lamps. If the brake was applied with the turn signal "on", the stop light current was routed via the turn signal/hazard switch to only the rear lamp on the side opposite the active turn signal.

Newer vehicles generally have the stop light and turn signal/hazard functions provided by separate lamps. Thus, the combine/separate function of the turn signal/hazard switch is no longer needed or present. As a result, you end up with five wires from the towing vehicle (r/s turn, l/s turn, tail, stop and ground) instead of four as described above.

This leaves you with two alternatives:

• add additional lamps to the trailer, or
• use a conversion device to selectively combine the stop and turn circuits.

Adding additional lamps is not a bad idea if space on the trailer allows. it makes the trailer more visible, and thus can improve safety. It also increases maintenance requirements. if doing this, you can simply add two more lamps -- one to each side. These lamps can be of either single or dual filament type, and either way should be mounted inboard of the existing lamps. The existing lamps should be used for the turn signal and tail lamp functions; the added (inboard) lamps should then be used for the stop lamp function (and tail lamp as well if dual filament lamps are used).

Using a converter eliminates the need for additional lamps on the trailer. Converters are commerically available at most trailer and/or boating supply houses. Or... you could build your own using a circuit **broken link removed**. I don't recall the original source of this basic design, but I have updated and clarified it, and I have added the standard trailer wire color codes as well.

 

[adell]

trailer wiring

Ive fixed this type of problem before. As electric current finds steel a bad conductor its better to have an insulated return earth system back to the battery end of problems 8)

 

[electric_ride]

I bought a very old trailer also ,I sandblasted it and found it was just easier to replace all the lights and wiring .Might be better for you in the long run .Good luck .ER

 

[mneary]

Three year old thread

 

[electric_ride]

oops sorry

 

[ericgibbs]

oops sorry

I expect the rust has got much worse during the last 3 years!