Trailer lights

test lights take a lot less current to light one little bulb and if it is a ground problem the test light may light up but it could still be the truck. The best way to find out witch on it is would be to hook the trailer to a different truck or you truck to a different trailer or you could use a battery and some jumper wires to the front of the trailer and see if the lights work.

The very first thing you'll nedd to do is determine if this is a truck or trailer issue. Get a test light. Start the truck, turn on blinker, and go to the tralier plug on the back of the truck. Put one end of your test probe (light) into the ground recepticle on the plug, take the other end of your test probe and touch the other nipples on the plug, one at a time, and see if you get your test light to blink. If it dosn't blink on any nipple you'll need to check the fuses in the truck to insure one isn't blown.

Once you determine that the truck is functioning properly, then we can move to the trailer for testing......

I couldn't agree with rob more. I work at an RV dealership and a lot of the new and used units we sell have an problem when we hook the trailer up. It is almost always the ground prong in the truck plug or a nasty ground on the frame. Having the trailer latched onto the ball will help with the ground but if that makes a differance in how your lights work you have a ground problem. The grould that the ball and coupler make should not be needed and the wiring should be sufficient. If the truck was a factory wire and some that aren't will have trailer light fuses. With no stop or blinkers it is not likly but easy to check. If it is a tilt traile you might need to add a ground between the toung and the main frame to help. Another very comon thing is corrosion on the bulb itself. If you truck has separate bulbs for running lights and brake/blinker it will have a taillight converter witch if it is after market they go bad all the time.

90% of all trailer light problems are ground related! check the ground on the truck if is is rusted (with the wisconsin and minnesota winter and a little salt will make this problem) clean it, (usually the ground wire is bolted to the frame of truck and boat) Same with the trailer it may look fine but reality it is not.

If you want to solve this problem is is very easy. run a ground wire directly from the battery to your trailer connections. and then run a separate ground wire from trailer connection to all tail and marker lights.

I run about five different trailers from fifth wheel to boat trailers. since i done this i have solved all of my trailer light problems. It may cost a little bit in the long run, but it will save time and money

dont hitch your tralier up. this way you will know when get a good ground. to make sure every thing is working properly

had the truck hooked to both trucks. same problem.

Actually hitch the trailer to the truck. Don't just back up close and plug in the lights. Depending on your setup, the ground may not work until the truck/trailer are physically touching metal surfaces.

My thoughts are its a grounding issue. Is the ball hitch new or very corroded? I've had the same problem and had to scuff up the new ball and problem solved. Just a thought.

just picked up a trailer with the same problem. Tried hooking up to separate trucks and still got no brakes or turn. ground appears good. Thoughts?

On my 09 f150 I have a separate fuse for the trailer brakes, the fuse kept blowing because of a short in the trailer wiring. There are two different fuse boxes one under the hood which is the one and another in the left kick panel. I also changed to LED lights much brighter.

Bumper, Did you ever get this figured out?

as my pop used to say - millions of years ago man invented the wheel, very soon after that he invented the trailer, and he's been tryin to get the lights to work ever since

Was your pop Patrick F. McManus?

Your rear bulbs have two filliments in them. One fillament illuminates the running lights. The other fillament illuminates the brake/turn signal. You could have the wrong bulbs (single filliment) in there. You could just have bad bulbs too. There are many possibilites to this problem, but I'd check the bulbs first.

Fuse

most trailer light problems are caused by a faulty ground.....as my pop used to say - millions of years ago man invented the wheel, very soon after that he invented the trailer, and he's been tryin to get the lights to work ever since

your ground on your trailer is not connected or you have a blown fuse on the vehicle side

I had this happen last week, The plug going into the truck was loose, all I did was wiggle it and everything worked fine.