My buddy has an 07 Street Glide and has the pigtail just as Jrsess describes attatched to the frame rail but mine doesn't. I wonder if the dealer removed it?

 

Careful, the accessory plug is exactly like the plug the dealer uses to plug in the diagnostic equipment. I found this out the hard way trying to add an accessory item. The accessory plug is up in front of the battery but can be hard to find the first time, you usually have to pull the battery out to locate it. It didn't hurt anything when I plugged my accessory into the diagnostic plug, my accessory just didn't work. My dealer told me they've had mechanics make the same mistake so I didn't feel so bad. Kinda stupid for HD to have the accessory outlet and diagnostic inlet to be exactly the same, guess they wanted to save a few pennies.

 

I just went through this last weekend. I had put some LED's under the tank and wanted them on the ACC switch. I checked at the dealer and there is 3 types of plugs available for my Ultra. There is one that is made to plug into the Acc plug located in front of the battery that has a split into two more of the same type of plug, one that plugs in and ends in a cigarette style plug, and a third that is made to hook into the battery harness that would be for something to have power all the time and not be switched from the factory switch on your fairing.

I was told that you can purchase all of the parts to make your own plug, but it ends up being more expensive that buying the one that splits it into two plugs. I think it was $15 or so. I decided to buy that one and just cut off one of the plugs and use it. I think that if you are a frugal type of guy you can probably search at Radio Shack and find the correct type of plug in a deutsch brand, but I was lazy and just shelled out the $15.