Installing a 7-wire trailer plug

[bryan_1980]

Hope this is in the right forum. I was wondering how to install a 7-wire trailer plug on my '99. It has the factory tow package. I have seen some 7w plugs that have a pigtail that plugs in to the existing 4w flat plug, with the additional wires hanging loose. Just wondering if anyone on here has attempted this before. All replies are appreciated

 

[manaen]

I installed one on my 2001 mounty, I needed to find the adapter for the harness, but once I found the correct adapter it all went smooth. If you already have the 4flat your halfway there. The other wires need to be run seperatley (ie brakes etc..) I don't think any gen 2 had the harness prewired for brakes, but I could be wrong. Mine did not..

Do you need all the functions of a 7wire plug? or just the lights?

 

[dogfriend]

You would probably get a better response in the towing forum.

I have a 7 wire plug on my Explorer. You are on the right track with the adapter that plugs into the factory 4 wire plug. That will take care of the lights.

IIRC, the other 3 wires are:

Blue for the Electric brakes - you will need to connect to the brake controller inside the cab

Black for Charging a battery on the trailer - I ran this wire up to the engine compartment near the battery, but did not connect it to anything because I don't use it. If you want to connect it, you need to provide a relay so that it is only powered when the engine is running or even better, use a battery isolator so that the truck battery does not get run down by charging the trailer battery.

White for Chassis ground - you should connect this to a convenient location on the frame.

 

[manaen]

if it is a good 4flat connector it should already have the ground connected, so all you need is a brake controller, unless your trailer has surge brakes, then you don't even need that.

 

[bryan_1980]

Thanks for the replies! I figured I would go ahead and do a 7-wire harness, so I'll be prepared for anything. Like dogfriend said, if I don't need one the wires, I'll run them anyways and just leave them disconnected. I'm mainly going to be pulling a little pop-up camper. Not sure what kind of harness it has, but I know it does have electric brakes. It'll at least be a 6-wire, I'm thinking. I found a kit on etrailer.com that has the 7/4-way plug, and all of the circuit breakers and stuff to wire a brake controller, too. Might not be a bad deal for $49.99+S&H.