I forgot the company, a google search may find it, that makes a direct wire harness for the Magellan as well as other models.

They have the voltage converter inline and you can direct wire to your Aux switch or directly to the battery.

It's designed to drop the 12v bike voltage down to 5v for the GPS.

 

Gilsson.....makes a power cord for all makes and has the converter built in. Google them and you will get plenty of hits. I bought mine from buy.com for 23.95 and free shipping.

I installed one fro my Garmin by just splicing into the orange lead on the ACC switch for power and just placed a good ground under the batwing. That way the GPS power cord is not hot all the time. I can use the ACC switch to power up or down.

 

on my 2008 road glide, i wired mine the hard way, i removed fuel tank ran the wire in the plastic wire trough, ran wire to fuse block, ground wire was installed on stud with other ground wires using eye connector, power wire was connected to empty slot in fuse block using adapter/harness-fuse block part #70329-04 and 2 amp fuse

 

You did it the FUN way, probbaly the way Harley runs a wire in the trough I bet.

I hate removing the fuel tank on my 07 RG.

I ran a 2 amp fused for my Garmin off the ciggy lighter, haven't had any problems.

 

Okay, just finished. Here is how I did it:

Fearing that the 12V plug on my GPS cord should not be cut off due to the voltage drop, I chose to add another 12V receptacle inside the batwing.

Bought a $3.85 12V splitter at Walmart made by Bell. What I was looking for was a 12V socket that had clearly marked +/- wires. This did. I cut one of them off which gave me a socket with about 6 inches of wire, which was plenty. Threw the plug away, and kept the other socket 'just in case'.

Removed the outer batwing shell (took ~5 minutes).

Ran the GPS cord out through the clutch line hole in the fairing which is near my GPS.

Plugged the GPS plug into the new socket, wrapped it neatly in black electrical tape, and zip-tied it to the fairing brace along with the excess cord. Used 3 zipties so it's rock solid.

Cut the wires that connect to the oem cig lighter about 6 inches back. Had to cut off the shrink wrap.

Used quality wire nuts to join the wires, folded them neatly and wrapped them in electrical tape.

Reinstalled the fairing outer shell and all works fine. Now the GPS turns off and on with the ignition or accessory key position.

BTW, when starting the outer shell removal, I found that one of the lower inner black machine screws was completely missing. Must have just vibrated out. I bought a couple more so now I carry a spare.