Need Help, Factory Trailer Lights

I have an '02 Explorer XLT with the factory tow package installed. It has the 7-pin plug and I bought an adapter at walmart that converts it into a 4-wire plug. The problem is when ever I hook up my trailer the trailer lights don't work. I have checked the 7-pin and it gets juice, I also plugged in the adapter and it gets juice; the problem is the juice fades away before it reaches the trailer lights. I know the trailer lights work, because they work when I hook it up to my dads '09 F-150. I'm so confused because when I hook up the meter it shows juice, I can even see the blinkers blinking, but nothing on trailer lights. Any help would be greatly appreciated.

 

[A Wise Guy]

How is your ground? On a side note did ford not do the 7 pin plug with the flat 4 under it and back a little like on the gen 4?

 

[thebrakeman]

I was wondering the same thing. Get on your knees to see if you have a 4-flat underneath from the factory.

If the lights work when hooked to your dad's truck, you know the trailer and trailer wiring is OK. You need to find out what's the difference between the F150 and the Explorer.

1. How much voltage at the 7-pin?
2. How much voltage at the factory 4-pin (if it's there)?
3. How much voltage at your 7-to-4-pin adaptor?
4. How much voltage at your dad's F150?
5. Is the F150 using a direct 4-flat connector, or your same adaptor?

Just keep experimenting until you find a difference. I suspect that for whatever reason, you are not getting sufficient voltage to the back of the Explorer, or that adaptor is bad.