My truck is equipped with the tow package and the 7-pin receptacle for trailer lights/brakes/etc. I have an electric brake controller in the cab. The ground (pin #1), left turn/brake light (#5), tail light (#3), right turn/brake (#6) and electric brake (#2) all work. As I understand it, pin #4 (2 o'clock) is used to charge the battery in the RV trailer. I checked the #4 pin with ignition on & it was dead. I looked at the trailer fuse (40 amp) in the power distribution panel under the hood and it looks good. Where else should I look for the disconnect? Also what is the auxiliary pin (#7, in the center) used for & how is it switched?Appreciate your help,Joe in St Louis

Re-check the fuse with ohm meter (DVM) I've found several fuses that are cracked and not blown...

Re-check the fuse with ohm meter (DVM) I've found several fuses that are cracked and not blown...

Mike, Can't say I've seen a fuse quite like those in the power dist. box before. I tried wiggling it & pulling it out but it didn't seem like it wanted to come out. Am I going about it wrong? Do you know if the power is switched by the ignition? Is there a relay that turns power on to that pin in the plug? Thanks for your help - appreciate your time!

Yes there is a relay to that. It's switch power. Should be the bottom relay of you looking at the line of them from the drivers side. Mine was missing when I tried to use mine.

Actually I hate to say it but that line is direct wired to the battery through that fuse. It should be constant hot and not switched.

With the help of Mike's wiring diagram I was able to trace the hot lead from the PDC back to the receptacle, and found a corroded, broken connection. All fixed now - Thanks Mike!The diagram didn't exactly match my '99. I found a pair of connectors behind the left front wheel well; a small one for the truck tail lights and a larger one for the 7 pin trailer receptacle. And my power wire was solid red as opposed to red/orange.Appreciate the help!Joe in St Louis