Bizarre trailer light problem

[23jayhawk]

The tail lights on our utility trailer work fine as long as the headligths are off. Brake lights & signals function correctly, and if I turn on the lights, the tail lights work also. However, with the headlights on, the signals work backwards and the brakes cause both tail lights to go out completely. I have always done a light check before we pull out, but to be honest this may have been the first time I happened to check signals & brake lights with the headlights on. What's the deal? :think:

 

[CanadianRidr]

Did you check all the fuses? Also are you running an adaptor for the connection between the trailer and vehicle? That may be the culprit :thumb:

 

[VintageDirt]

How good is your ground connection?

 

[BSWIFT]

I had the same thing happen to me with the quickie type "factor" plug in 4 way flat. The package said it fit my truck and everything worked fine until the headlights went on. I hated to splice into the wiring but I did and solved the problem.

 

[clutchcover]

I vote for the ground also. I had problems with my dash lights and tach. When I would turn on my dash lights, my tach would stop working. The ground had come loose. It is a different problem, but same theory. If it isn't your ground, you can probably get someone else to butt in and offer an opinion.

 

[justql]

The majority of trailer light problems are grounding issues.

 

[bnr]

25 years ago I worked at a trailer hitch shop. We use to turn on the head lights and then step on the brake. If the lights went off it was ALWAYS a grounding problem.

 

[23jayhawk]

Thanks, everyone - great responses & quick. I'm not an electrically savvy person, so grounding would not have been a direction I would have gone. Will check it out this weekend & report back.

 

[jmics19067]

How good is your ground connection

I vote for the ground also.

If the lights went off it was ALWAYS a grounding problem

I am going to say the ground also the stranger the problem the most likely a bad ground is the culprit. if you have a complete circuits go down while turning on an other most likely the trailer isn't grounded to the vehicle. if your body lights and or brake lights flash the opposite of your turn signals it is most likely a bad ground around the area of the turn signal light that acts funky.

a quick and easy way to check the problem is to take a pair of jumper cables and just connect the trailer to the towing vehicle. If the lights work better you know that the trailer isnt grounding to the tow vehicle properly.
Or take a test light ,turn on everything that gives you a problem and connect the test light between the trailer and truck. If the test light lights up you have a grounding problem.

situations like this can cause your cruise control not to work properly also, a bad bulb or ground on your brake light can cause the elecricity to back feed thru the brake circuit making the cruise control think you brakes are on.
<took me a long time to figure that one out :debil: >

 

[RM250'er]

Ground

 

[23jayhawk]

So like I was saying, of course it's the ground :)

Left is left and right is right, and when I step on the brakes both sides get bright. :thumb:

Grazi!