My 1999 F150 came factory installed with a 4-pin connector. I now need to tow a trailer with trailer brakes. So I want to upgrade to a 7-pin hookup. I disconnected the 4-pin hookup wire assembly from the harness (hoping to be able to simply replace the 4-pin wire assembly with a 7-pin wire assembly); However, the harness has only five pins. So I am now thinking there is more to it.

Does anyone know where I can get some instructions on how to do this?

Or, could anyone give me high-level instructions on how this is to be done?

Or, has this answer already been posted and I just not see it?

 

That is odd, on my 01 I simple removed the 4-pin harness and put in the 7-pin harness. I would think the 99’s are the same as the 01’s as far as it is wired for 7-pin just an option to add the 7-pin in. Could call the dealer and ask.

I needed mine for the same reason to tow a pop-up trailer so needed the 7-pin to be able to charge the battery on the pop-up trailer and brakes. You most likely have all the fuses but will need the relays. Since you only had the 4-pin like myself you won’t have the relay for the battery charge which I believe is the same for the electric brakes. Check your owners manual for the location and then check if you have them. If you don’t you can get them from the dealer, mine were not a bad price I think I paid $4 - $5 for the relay.

 

The relay is already there. I'll purchase the 7-pin harness and give it a try.

 

check "towing and hauling" more info there...Good Luck.

 

Picked up the 7-pin harness from a dealer; the price was actually better than many online retailers. Nice thing about this one, it comes with a 4-pin connector also. As stated above, it ended up being really easy to replace/install.

Thanks for everyone's help.

 

That's right I forgot is already had the 4-pin as well. I too bought my 7-pin at the Ford dealer. I only did so to make sure it was the right one, wired correctly.

It is good to hear it worked out for you...