DaySailer.org Forum

The PO of my DS2 installed a light bar for the trailer lights. When I cleaned up the wiring harness, I noted that the ground wire is an essential part of the circuit. No ground connection, no nothin'. The system works fine after cleaning contacts, etc., but I'm puzzled by the circuit arrangement. If the ground is for safety, why then will loosening the ground interrupt the circuit. Since the source is a "flat four", with the three color coded wires and a ground, where is/are the return wire(s) that completes the circuit? Or is the ground the return? Inquiring minds want to know. Thanks for your help.

the ground wire (absolutely essential that you have a good ground) completes the circuit, the other wires (hot) are for your tail lights, left signal/brake and right signal/brake

Direct Current, such as used on a car, trailer, or anything with a battery, only uses 2 wires to complete a circuit. You have your positive post & negative post on a battery. The negative connects to the chassis of a car, and the positive is distributed throughout the vehicle through fuses, switches, relays, etc. If you took a DC light bulb and connected it from the positive terminal of the battery to the negative terminal, it would light. There you have created a simple DC circuit. Every circuit in the vehicle is based on that.
When you connect a trailer to the hitch of your car, the tongue & hitch make a ground connection, but this should never be relied upon. The minimum amount of wires needed is 4, as the previous poster said; Running lights, LH turn, RH turn, & Ground (the LH & RH are used for stoplamps also). If you have four separate light bulbs in the back, one on each side will be used for running lights, the others will be used for their respective turn/brake lights. If you only have 2 bulbs, they are dual filament, and can only be installed in one direction.
This may be more information than you need, but when it's how you make a living, sometimes it's fun to share.

I recently rewired my trailer. It had been jury-rigged so that the brake and turn signals only worked in the rear, not very brightly, and the nighttime lights didn't function. In fact, if the lights were turned on, the rear brake and turn signals didn't function. Same issue as yours - I couldn't see that the ground wire was connected anywhere.

I bought a new harness and rewired it according to the diagram like this one

http://www.skiboathelp.com/tech/t_wiring.html

and all works fine. I made sure to properly connect the ground wire to the hitch ball coupler, and sanded all metal surfaces to ensure good contact. I wired it outside the trailer frame first to confim that all was as it should be, then ran it through the frame. It sure is nice to have a fully functional system that is as bright as it should be.

Carlos

Thanks for all your help. I forgot about the differences between DC and AC.

I recently rewired the Red Witch's trailer. Before, there were lights that had to be clamped to the transom, which was a pain for a dry-sailer!

I wanted to isolate the wiring, so I ran the ground wire all the way back to the lights, which are two simple submergeable dual-filament fixtures mounted on PVC "outriggers" that are screwed into flanges mounted on the bunks. The left side one has a bracket for the license plate.

Sorry to report that the sailing here in Volusia county hasn't been too great lately, as we're finally getting the rain that we've been begging for. Too bad that rain comes with lightning, too! Yikes!

- Tim