Pete-
Trailer wiring diagrams I like best:
etrailer
They confirm that "standard" 6-pin center would be trailer charge line.
Winnebago wiring diagrams for your coach are available via this tree:
Winnebago Owner Resources
Guides and Diagrams
2005
Minnie Winnie 27P
While you're at the 2005 link snag a copy of the "
Wiring Identification Guide" (secret decoder ring)
On the 2005 Minnie Winne 27P wiring diagram Table of Contents, open the "
Body, 12 Volt Wiring Diagram." Sheet 1, Zone A-10 shows the center pin is fed by Winnebago circuit AAE. Sheet 1, Zone A-8 says AAE is fed from Ford wire, colors black/light green. Secret decoder ring says AAE is "FORD CHASSIS TRAILER BACKUP LAMP CIRCUIT (BLK/LT GRN)." The backup circuit.
What does the
2005 Minnie Winnie operator's guide say? Page 15-4 (112 of the PDF file) says the center pin is the backup circuit.
Over to the Ford side.
Ford 2005 Body Builder Layout Book (tree is: "
Publications," click "Body Builder Layout Book," click "Show More," scroll down to 2005 BBLB), page 169 (which is page 166 of the PDF file- don't get confused!) shows the E-series trailer wiring. Except for an error there, the diagrams and tables confirm that black/light green, Ford circuit 963, is the trailer backup lamp circuit.
So, we have three confirmations that Winnebago wired the center pin to the backup circuit. In their defense, I seem to vaguely remember that was an early "standard." I could be incorrect!
What to do?
Look again at the BBLB page, the middle illustration. Inside the left frame of the coach, about three or four feet from the rear of the coach, are three Ford connectors. The round one feeds the coach lights. The two half-round connectors feed the trailer. One of these two has three wires, the other four. The three-wire connector has these wires:
Trailer backup lights: black/light green
Trailer electric brakes: blue
Battery: orange
The last is the trailer charge line.
Your assignment, Mr. Phelps ("should you choose to accept it"), is to wire the orange wire to the center pin of the coach hitch connector.
Follow the wiring forward of the coach hitch connector until you find the Ford connectors. In both you will find pigtails (provided by Ford to Winnebago) connected to the two half-round connectors that are attached to the frame. Carefully unwrap the electrical tape on the pigtail attached to the three-wire connector. Inside you will see the black/light green, blue and orange wires. The first two should be connected to Winnebago wiring and go to the 6-pin hitch connector. The third, orange wire should be unterminated.
Butt-splice a 10 or 12 AWG wire onto the orange wire and extend it to the coach 6-pin connector. At the connector, remove the black/light green wire on the center pin and install the orange wire in its place. Insulate the black/light green wire, tuck it out of the way, re-tape the pigtail and you're done.
Use an exterior-rated butt splice or cover an interior-rated splice with heat-shrink tubing. Despite the electrical tape those splices can attract moisture and dirt and fail "silently" later on. Please don't use ScotchLock (a.k.a. "suitcase") connectors and please don't splice into the Ford wiring upstream of the frame-attached connector- use the pigtail.
<edit>I took a second look- It appears there's a disagreement on wiring between the diagram and the operator's guide re: the trailer electric brake wire. That got me second-guessing myself. So, you may be best off tracing the wires to the connectors first, and letting us know what you find, rather than diving in with the confident instructions I gave above, wire and splice tools. It has to do with the "X" wire in the diagram... and, if you find the trailer electric brake connector wire missing at the hitch connector... Anyway, let us know what you find.</edit>