Can someone help? All the functions in the 7 pin connector work fine except the 12 volt aux power. Anybody got an idea how to fix it?

 

Have ye looked in ye Owner's Guide yet?

Refer to pages 341 & 342.

Check to see if Relay #9: "TT Battery charger relay" is present/healthy

Check to see if Fuse # 21: "TT battery charge relay power" is present/healthy

Check wif a meter, not just ye Mark 1 Eyeball.

G'luck

 

Are you checking the trailer tow battery charge circuit with the key in the run position ?

The relay noted above it not activated, unless the key is in the run position.
Fuse #21 is hot all the time, but Fuse #5 to the trailer tow battery charge relay coil is only hot in the run / start positions and the BCM activates the ground side of the coil on the relay.

 

Thank you, I did look at the owners manual and low and behold both relay #9 and fuse 21 we're not installed. Why I don't know. But I swapped them out and the problem solved except that my local Ford dealer does not stock either fuse or relay....wtf.

 

Those parts should have been in your glove box.......Also, look under the back seat or the owners manual envelope.

 

I had to install them as well when I upgraded to the factory integrated brake controller. They came in the "kit" with the controller