I am rather dissatisfied with the aftermarket t-connector that hooks into the wiring of my bronco. I have a trailer that I have went complete through the wiring at least twice, and I get weird connections like when the taillights are on and my brake lights are on I get the back up lights to come on on the truck. If I disconnect the trailer and have tail lights and brake lights on the back up lights stay off. Actually the lights work perfectly up until I hook the trailer in to the truck's wiring. While trying to fix the mess of wiring with a new mess of wiring; I found that there are two pig tails at the same point that look like factory connections for trailer lights. I am not certain and have not yet tested this theory, but did these trucks come with the factory pigtails to hook up tail lights and brake controlers for trailers?

 

I know that the 1986 model did not come with a factory pigtail, one of those tee adapters was required to make a clean install.

If you are having the problems as you describe, it sure sounds like a bad ground. To make a quick test, take a set of jumper cables, one clamp to a clean ground point on the frame of the Bronco (NOT the hitch) and the other end to a clean ground on the trailer.

Please post the results - and we will see where to help you from here. David

 

Must be a bad ground in the truck then, because I ran the ground wire into the loom and avoided the whole grounding to frame and tried to get it to the truck instead.

 

It could be a bad ground on the truck, I have experienced that before.

Another thought - you have single bulb (but dual filiment) tail/brake lights on both the Bronco and the trailer? right? Something like #1157 bulbs, at least on the trailer.

David

 

I figured out that the ground on the back of the truck is not going to the trailer lights by hooking a temporary ground on the trailer light wiring on the vehicle side to the frame of the truck. I will have to go find the grounds on the body and probably clean them up and make sure they have not corroded badly.

It is the dual filament 1157 bulbs on the trailer and the newer style dual filaments on the truck side, i.e. non-push in and twist 1157 but plug into the harnass type.

 

cool, suprising what type of problems show up with a bad grounds.

David

 

When I wire a truck or trailer up I always run a 10 gauge wire to the truck frame from the plug on the truck and a 10 gauge wire directly to the trailer frame from the trailer connector. You would be surprised all the problems you get from a poor ground point. One last tip is to always use a star washer.

 

I agree. When I tow something that I normaly do not tow, I always have my jumper cables at the ready, they make a great ground connection between a trailer I might only tow once and my truck. Nice big jaws to cut right thru paint, rust, etc to get a good ground!

David

 

Actually found out why I had a poor ground. The wire that the aftermarket t-connector had as I assumed to be a ground wire into the truck system was not a ground wire. That wire was for the lights for the backup lights for the truck. I always thought that ground came off the one side of the flat 4-wire connector but not so in this case. Sorry for the confusion and just restating that just because you can buy it doesnt mean it is right.

 

I wire everything 7-wire. It has a ground wire more than adequate for the job. I know someone is going to say that they don't run 7-wire on their trailer. You can adapt a 7-wire RV connection to anything except a 7-wire semi connection. In fact I went to the store today and couldn't even find a 7-wire connection for on the truck that didn't have a 4-wire built in.

 

We only use the seven pin semi connections on our equipment, large or small. Those boat trailer that come with the flat 4 I make up adapters for.

We do this so if we have to use a third party trucking firm to move our equipment, the lights will hook up, plus it makes everthing universal, we might tow a 14' skiff behind a 70bbll 53k Kenworth Vac truck for example.

Still, I always carry my "extra" ground jumper cables, they have saved me many times.

David