My trailer brakes do not work when the ball and trailer make a connection. But if I just plug in the trailer to the truck I can hear them working. I have checked everything and have had others look at it. Can anyone please steer me in the right direction?

the wires to the electric brakes at wheels , I had this problem on my travel trailer and it turned out due to corrosion at connectors at wheels the power wasn't getting to wheels one other thing to ck is trailer plug , it turns out not all mfg wire there plugs the same , try to obtain a diagram from mfg for both trailer and truck , compare them for any differences

Hi Bruce,

Let's back up for a second. Are you wired like this?

http://www.countrytrailer.com/uploads/7wayplug.pdf


Using an inexpensive 12 V test light / tester like the one below, connect the clip to a good ground on the vehicle. Then with someone else working



the brakes, turn signals, lights, etc. ONE AT A TIME, you should push the point end of the tester into the corresponding connection on the VEHICLE. Only one connection should have power at any given time. Once you have verified that the correct & only connection has power at the right time - you can move to the trailer end of the wiring. If you can not verify the vehicle plug is working correctly - you'll have to get it working right before continuing. These connectors can develop problems over time and may need servicing.

If the trailer still has issues, check ground by uncoupling the trailer hitch from the ball on the vehicle. Keep the 7 pin connector from the trailer plugged into the vehicle and turn on the vehicle lights / have an assistant step on the brake. Connect the clip to the frame of the trailer and push the point to a good ground location on the vehicle. If the tester lights up - you have a bad ground wire between the vehicle wiring to the jack and the trailer frame somewhere. The lighting is relying on the contact between the ball & hitch for ground and could be causing the problem.

Check all the bulbs to make sure that they are the right ones and if the offset bayonet base type - inserted properly. Inspect lamp sockets, wiring and ground leads at each lamp socket. You can also disconnect a wire from a point that is common to left and right sides of the trailer to help narrow down where to look on the trailer for the trouble. If you disconnect a wire going to the left side and everything on the right works as expected when trying all the lights, brakes, etc. then you know the problem is probably on the left side. Reconnect the left side and disconnect the right side and test again. It is a process of elimination when you can't see anything obvious. Keep disconnecting 1/2 of the side that is causing trouble until you find the problem.

You can purchase a 7 wire vehicle jack test plug like this to quickly diagnose the vehicle for less than $10. It will indicate on the LEDs the power seen from the vehicle.

If all the lights work properly with the trailer wiring not connected then the truck itself is fine. If attaching the trailer wiring causes the lights to permanently stop working on the truck then you are blowing a fuse and it will need to be replaced. Your owners manual will show you where the fuse panel is. You should be able to check the wiring plug at the back of the truck to be sure it is working properly with a test light and a helper. If the power for signals/brakes etc are not all working at the plug, then trace back and fix these. If all is good at the truck's plug, then the trailer wiring must be faulty. Again, go through it and fix anything that is broken or corroded. Of course it goes without saying, make sure all the bulbs are good.

Do you have it hooked up to the ball when you are testing? 4 Leads covers L+R turn (2) Brake (1) and Running lights. You don't have a ground.

some van don t have a ground wire. hook up to trailer put jumper cables to frame of trailer and van if works install a ground wire plug

Headlights must be on for the interior trailer light to work.

Check this location. They have color codes and wiring diagrams. Make sure the trailer has a good ground. It MUST have the ground wire connected to the truck and trailer or you will have a floating ground through the ball. That will cause blown fuses. http://www.etrailer.com/faq-wiring.aspx

wires on truckhave a feed ,are they connected correctly??

When the trailer came off and pulled the light cord it stretched or broke wires inside the trailer harness. Start tracing back from the plug, paying careful attention to sharp bends and hold down points as well as connections. Remember that wire could pull apart inside the insulation without breaking it. It might be just as easy to replace the tailer harness. Hope this helps.

Take a 12 volt test light... the kind that has a spring loaded clip to hold the probe into the wire, and insert it into the wire just before the trailer plug, vehicle side. (Blue I think) If there is a connection, the brake should see it and you should have an indicator light. When you activate the brake the test light should lite up. If not, move up to the brake actuator and test the blue wire. If there is nothing at the actuator, check the black wire. It is power to the controller. If no power there, check fuses again. If it does pick it up at the plug, connect the trailer and test the trailer itself. First ground to the trailer and then to the truck. Most problems are ground wire related. Then move to the axle and test it there. For the brakes to work, and even show on the indicator, there has to be a ground and power to the brakes themselves. There are 2 wires to each brake... a ground and a power. Test across both wires to make sure you have power and ground. You can also hook another trailer to your truck or another truck to your trailer. Lights can work through trailer ball ground. Brakes can't. leave the trailer unhooked from the trailer and hook the wiring up and test the lights. That usually will indicate a good or faulty ground. Also make sure there is a GOOD ground to the truck frame/body. Also try http://www.etrailer.com/faq-wiring.aspx. They have a great website with lots of info. Hope this helps. Mike