Trailer Plug wiring problem on 2000 Chevy Silverado

I had a flat four prong wiring harness on my truck when it was rear ended in an accident. The body shop installed an OEM Reece Hitch and wiring harness. Now when I turn my turn signals on it back feeds through my brake lights and if I turn the left signal on both sides flash and the third brake light on the back of the cab flashes. I cut the brake wire on the plug so it would pass inspection but now that it getting warmer I need the brake lights to tow the boat and camper. I have moved from the area where the bod shop was located so I can't run it back to the shop for them to work on. Any suggestions on how to re-wire 7 way plug or to trouble shoot this problem would be appreciated.

 

Welcome to the forums.

You were using a 4 pin plug before and that worked fine...... correct ?

Now they have installed a 7 pin plug and there are issues.
How do you connect your trailer to the 7 pin plug ?

The 7 pin plug is not hard to wire up but we need to know if it came with the wiring that is color coded or did the garage add the wiring to a 7 pin plug.

 

The shop added the 7 pin plug, the four pin plug seemed to work fine. I never had a problem with the lights doing this before, but I don't think I had brake lights. When I hook up to the trailer I use a Hopkins 7 to 4 adapter.

 

Could be a bad ground connection.

 

Checked the ground and made sure it had good contact on the frame and I still have the same problem.

 

I've been out of the mobile loop for a while but I'm pretty sure your vehicle uses combo brake/directional lamps.

Try this...... put the left flasher on and have someone hit the brake. The left side should flash and the identical lamp on the right should be on solid. And if you switch side the opposite would be true.

This means you have a basic four wire system and the trailer wiring should be fairly straightforward. The four wires are left directional, right directional, parking lights and ground.

I used to buy the plugs and jacks in bulk and wire them myself. Your vehicle mounted 7 pin jack could have the correct colors on it and that would mean you would be using green, yellow, white and brown.

Since that vehicle already had a trailer connection wired in you should be able to find all 4 of those wires in the harness at the center of the vehicle behind and above the bumper. Actually the white from the plug would go to black in the wiring harness.

A 12v test light makes the wire locating job much easier.

 

The trailers are already wired, the problem is in the truck. If I wire the brake lights into the turn signals when I put on left turn all the brake lights blink on the truck.

 

I understand that. Did you try what I asked above about putting the directional on and hitting the brake ?

 

Yes, the brake and turn signals lights work fine on the truck, but there is no juice going to the brake lights for the trailer.

 

Yes....we know the vehicle is ok.

Some vehicles require a convertor to convert a 5 wire switching system to 4 for the trailer. I don't know if you require a convertor because you haven't answered my question yet.

Try this...... put the left flasher on and have someone hit the brake. The left side should flash and the identical lamp on the right should be on solid. And if you switch side the opposite would be true.

On some vehicles the brake lights and the directionals are different lamps. In that case a convertor is required.

 

sgt1975,

I would like to help you, but it seems like I’m missing something. Can you please clarify the one question I have Thank you?

Prior to the accident the 4 pin harness worked fine. So why did the body shop install a 7 pin harness, and not a new 4 pin harness?

Thank You
Amy