I just rewired my 20'deckover trailer. I used good quality lcd's. I have the 7 and 4 pin plugs. everything works but the parking lights on both plugs. I have a 2006 f-150 extended cab. bought a test plug and its telling me my parking lights on the truck side are not working. any suggestions? thanks Lou PS I hooked up my 1986 dump and all lights worked fine,go figure

5 pin trailer connections here went out when Noah died. They were standardised at 7 pin for a long time then for a short time there was 7 + 1 and even that didn't provide for reverse lights.

Some 30-odd years ago there was a return to a single 7 pin for trailers with an additional 7 pin for caravans, the two designated 7N and 7S and the supplementary plug provided facility for caravan battery charging, a 12 volt supply, additional grounds and reverse light.
Today the standard Euro 13 pin system is creeping in.

Although it is impossible to buy a 5 pin trailer plug/socket here, I understand it is permissible to use one in the case of very small trailers where a following vehicle can clearly see the direction indicators of the towing vehicle, though that still would not facilitate the connecting of a reverse light as obligatory lights must take precedence, the rear fog light being required as well as separate circuits for left and right tail lights so with a ground, stop lights and direction indicators = 7 pins.

I find that the easiest way to fix this is to by a connector that is already wired for this situation. They are available from good auto spares shops. IT saves having to rewire the plug every time you use a different trailer set up.

Pull one of your tailights on truck, and find wire to back-up on it, then run jumper down to 7 pin plug. Might save a lot of trouble/time.

Not sure which part you mean no power.

For the New Body style 2004 ( not a Heritage or Lightning model )

If both Stop / Turn pins & the parking lamps, might want to check the ground pin to make sure it is good ( or what you are using for ground on the test light / meter ).

The trailer tow parking lamp circuit is fuse #10 to the parking lamp relay

The stop / turn circuits also have fuses on each one, Fuse #36 & Fuse # 42 ( R & L ).

The 7 pin has fuses for the battery charge pin ( hot in run position ) and the reverse circuit ( hot in run & when in reverse ), Reverse is also fuse # 10 to the trailer tow reversing lamp relay & the battery charge pin is fuse # 106 to the trailer tow battery charge relay.

Could be all the fuses are blown, or what you are using for ground on the meter / test light is not a good ground.

Check fuse 28 in the fuse block under the left side of the dash. There is also a relay for the trailer park lamps in that same fuse block. The fuse and relay are the trailer parking lamps and run independantly of the vehicles parking lights. You can also try backprobing the other trailer plug (you should have one 7 pin and one 4 pin) to see if there is power at the park light pin. If there is power at the other trailer plug than the fuse and relay are bad and you may have a bad/corroded plug or bad wring to the plug that doesn't work.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

you may have put wire in wrong terminal in plug

Suspect 7 pin connector problem , you should have power on the 8pm positioned and the centre pin position as you look into the socket (on vehicle. These pins are both male pins as you look at them . If ok check trailer wiring where it splits for either lamp assy ! Good luck

The trailer tow adapter parking lamps is fuse #10 in the cab fuse panel. There is also a trailer tow parking lamp relay that powers them, which could have a problem as well.
Start with the fuse, and maybe check both the 7 pin and the 4 pin for the parking lamps, could be a corroded pin on one of them causing the tester to not see the power on the pin.

Hey Boon,

The pinouts for a 7-way plug are as follows:
Seven wire Trailer plugs:

Horse, stock or utility trailers:
White = Ground - 1
Blue = Electric Brakes - 2
Brown = Tail and clearance lights - 3
Black = Battery, aux power - 4
Yellow = Left turn/Brake - 5
Green = Right turn Brake - 6
Orange or Purple (not both) = Auxilliary or Reverse - 7

Recreational Vehicle:
White = Ground - 1
Blue = Electric Brakes - 2
Green = Tail and clearance lights - 3
Black = Battery, aux power - 4
Red = Left turn/Brake - 5
Brown = Right turn Brake - 6
Yellow = Auxilliary or Reverse - 7

In both cases 4 is battery and 7 is reverse, aux or not used.

Double check your wiring using these lists as a reference.

Click here for my post on Trailer wiring

This should get us closer to the answer.

Best regards,
Mike

My 2004 f150 has the factory tow package. It has a fuse for the trailer running lights seperate from the truck running light fuse.
Check, you may have the same set up...