Trailer Plug Shorted?

[bdawson11]

I've gotten different answers from neighbors. I'm wiring up lights for my towable. I noticed that when using a light tester probing say the running light prong of the plug ( the plug on the back of the coach) I have found I can ground to any of the other prongs in the plug (brake, turn signal etc) and use it as a ground.

Is this OK?

I thought the other prongs would be for supply power to their respective lights and not go to ground at all. Thanks for your input.

[dickandlois]

dawson11,

Welcome to the Forum!

You are reading what will look like ground, but the reading you get (light turning on) is going through a bulb filament. Use a multimeter set on ohms - with the lights powered off. You can then see the slight resistance difference between the true ground point and the circuits.

You need a direct ground point from the plug designated as the ground.

This pin is connected directly to the chassis ground.


Rich.

[dave111451]

Rich is 100 per cent correct.

[bdawson11]

Thanks for your clarification.My towed vehicle lights were very dim found I had a bad ground all is working now.

[hermanmullins]

On every 4 way plug there is a white wire. It is the ground and for some reason it is always very short. However it is a very important wire. Too many folks just leave it disconnected, saying , no problem it will get its ground through the hitch. (as well it can). Then they go and cover the ball in grease, kill the connection and wonder why their lights are dim or don't work . Always connect the GROUND wire.

A loose or bad ground has caused more problems in homes, cars, boat trailers and RVs, then any one can imagine.

Herman