Got no trailer lights

My 05 cottrell has a in line fuse near the front left of the trailer. It also has one on the left side of the head rack. I have had that fuse holder get corroded.
Good luck!

 

Get yourself a good test light. Start from the light cord and work back. But First...Check to make sure the light cord plug has juice from the tractor, all pin holes.

 

Run a temporary ground wire from your tractor body to the trailer body, if the marker lights light up then your trailer socket has a short, croded or loose connection.

 

I always start by spreading the pins in the trailer socket. Since the 4 ways work it is not a ground issue.

 

Pull the lights out of the taillight boxes and check for a bare wire touching the box. Also check your marker relay for corrosion by switching for another relay of the same amperage.

 

How did you test power from the tractor? Always test voltage with the circuit loaded. It is very common to have corrosion making a very high resistance. High resistance will show battery voltage in an open circuit, but drop as soon as you try to power anything. Test lights just suck, use a volt meter. If you can't test it loaded, get a set of loading test leads or rig up a headlight bulb to make your own.

When you are sure that you have good power coming from the tractor, and your sure that the trailer has good ground, then move on to the trailer. Follow the 7 way, Cottrell usually has a plug under the front plate, sometimes it's a little further back just before it goes into the rail. It common to corrode there. The there is another plug in front of the axles, this is a Y plug that splits it off to the ABS, another common place for problems.