Dim/Bright Trailer Lights

[Mohavekid]

I Need some help here.
The lights on my trailer start off bright and then over 20-30 minutes they go very dim, you can barely seem them burning.
After a few minutes of being very dim, they suddenly go bright and start the whole dimming process over again. It happens to all the lights on the trailer at the same time.
This is something that just started happening last year. I've checked the plug and ground and all seem to be making good contact.
Any ideas?

[Rexone]

More than likely you have a loose, dirty, or poor ground connection and not necessarly at the plug. Check all ground connections, trailer frame, truck frame, any splices, etc. Plugs get old and worn too. Seen it many times.
Also if you're grounding through the trailer ball without a ground wire that can become a real iffy deal with grease or the accumulation of corrosion under the ball or in the receiver. A ground wire should always be present from the trailer to the vehicle.

[Jordy]

I hate to do it but I have to agree with Rexuno. Bad ground was the first thing that came to mind, even reading the title of the thread. Are you running a ground through the trailer plug or just relying on the connection you get from the tongue to the trailer hitch? There's a pin on most of the round plugs for a ground and it will fix all your problems. :wink:

[Checkmate]

#3 for a bad ground.

[Mohavekid]

Thanks guys, I run a 4 flat plug.
The ground to the truck is through the hitch.
I'll re-check the ground and see what happens.

[Jetmugg]

I vote for a bad ground also. It could be almost any ground connection between the lights and the trailer, or the trailer and the truck. Check every one, make sure they are all clean and have a good tight connection.
Steve.

[Havasu Hangin']

I agree it's probably a ground.
To check it...next time it acts up, run a ground jumper wire from the trailer to the truck- if it fixes it...it's the ground- if not...it's the power wire.

[UBFJ #454]

If not a grounding problem ... check the insulation on the wiring and see if there's not a slight worn spot causing a transmittent short ... ???

[Doug H.]

I had this problem with my old DiMarco boat trailer, and i found it to be one of the three center lights in the middle at the back.
The connection came loose and grounded itself on the trailor while driving, make sure all connections on the back of each light is secure. Hope this helps.

[mgar_red]

Mohave, does it affect the tow vehicle lights also? If so, you definitely have a shorted power wire.
Helped a buddy of mine re-wire his trailor after same symptoms and all grounding double checked. Come to find out it was inside the frame tubing where the wires ran which was not visible.