No trailer brake lights!

[nhproxr]

Buddy and I are planning on going snowmobiling up north this coming Sat. Problem is he hooks up to trailer and there are running lights, but no brake lights or directionals. Brake lights and directionals work on truck but not trailer. Truck is a '02 Z71 Avalanche. Since running lights work I'm assuming its not a ground or trailer wiring issue.

[mcreyaufmiller]

I would check trailer wiring first. If you want to check the trailer harness on the truck, get a multimeter, ground the black probe and set the meter to DC voltage. have some one step on the brake and check the pins, one of them should read 12+ volts, then do it again with turn, and running lights. If the harness checks out, go to the trailer. The is the most common place for problems, not the truck.

[nhproxr]

One thing I forgot to mention is his third brake light isn't working either, thought brake lights are run off that circuit. So maybe trailer is popping the CHMSL fuse????

[davegee]

Remember that the 99 and up trucks have seperate fuses for trailer and truck wiring, so have a look in your owners manual and check them...they are often blown by faulty trailer wiring

[pm26]

Remember that the 99 and up trucks have seperate fuses for trailer and truck wiring, so have a look in your owners manual and check them...they are often blown by faulty trailer wiring

 

Make sure the receiver hitch tube is not rusty inside and the drawbar makes good contact with the hitch.

 

I just wired a small new trailer and tested the lights on it. I just connected the trailer wiring four terminal plug to the trauck trailer plug 7 to 4 adaptor. Everything worked except the brake lights. Then I hitched the trailer to the truck and tried the brake lights and they worked. Go figure.

[redvett]

You cannot use the hitch for a ground you must use a separate ground through your trailer harness. Using the hitch as ground will cause the lights to flicker as you go down the road and the ball looses ground.

[mxzeatr]

I would check the trailer fuses under the hood, there are trailer brakes, running lights, blinkers etc....They are all fused in the main fuse box under the hood....The first time I hooked up my trailer to my truck the left blinker wouldn't work...Bugged the crap out of me, and it worked on our other vehicles, thats when I found out about the fuses....

[steveR]

2 beer job-

 

Clean clean clean. Testing is of no use unless your connections are clean. Clean your truck plug. I have a 02 z71 burb, lifted the flap, all the contact were dull and/or green. A little sandpaper and electronic spray cleaner, and presto shinny and new. Now sandless, dirtless and saltless. Do the same on the trailer plug. Be careful cleaning the truck with a wire brush, some of those contacts are powered all the time. Sparks and fusses. Next check your bulbs in the trailer. There is often a little corrosion inside the bulb socket. The little wire brush on the Dremel works well here. Your friend is dielectric grease. After you have cleaned all this, a little of this goo will protect your hardish work. On my big RV plug, I try and put a bucket over the tongue and plug to keep it out of the elements. All these problems seem to occur just before you head out, trailer loaded, kids in their seat, dark, cold, raining or snowing. If all else fails, change the bulbs. They are fifty cents each, and are often broken or loose and you cannot tell. You need a pocket of them anyway in your emergency kit.

[95Sierra2500]

I'd definately check the wiring on the trailer, as well as clean all your contacts and check your bulbs. It sounds to me like you have bad bulbs, bad connections (not ground, since you obviously have that), or perhaps you aren't even connecting to the brake/signal lights through your plug.