My trailer has lights, no turn signals, no brake lights. Towed it with my wifes Suburban all was fine. My 1997 F150 has worked with other trailers in the past, but it has been years.

I checked the relays in the samll box behind yhe large power box under the hood, it has 5 relays, 2white side by side, a larger black one in the middle and 2 more white side by side.

If I take out the 2 white ones close to the engine the flashers on truck stop, if i take out the large black one nothing changes, and when i take out the 2 white near the fender i loose the trailer lights,(these 2 ALSO SEEM VERY HOT). This box is not in the owners manual.

Any ideas?

 

Are you using the stock wiring harness? These things are prone to corrosion and not working as a result.

You may also want to double check the connections on both the pickup and the trailer. Something could have worked loose recently.

 

Hi Doc Welcome!

At least you knew about that small fuse box. I dont have that 97 info. what relay/fuse etc. Maybe someone here can update.

If you already fixed great...if not..have you tested the 7pin? plug on truck? Test each pin..then start checking forward from there.

could be where wires attach to each pin (from back side)
harness connections..bad ground etc.
Be sure you have checked ALL fuses/relays that go to plug. Are all the relays/fuses in just one box?

Trial/error...probably something simple...usually is.

Good luck...OT

BTW...truck/trailer wired same (plugs) right?

 

Thanks for the replies!

I have a factory 4 prong plug. I looked back in previous posts and found a mention of the even smaller fuse box closest to the fire wall (it holds 7 minis). I found 2 fuses and the second, 20 amp was blown. Does anyone know what the other, #1 5 amp is, or what the other slots are for?

Thanks,
Doc