Just got an 03 FLSTF. There is a plug hanging from beneath the seat on the left side. I figured it was for a battery tender to plug into. After looking at heated vests online, I notice what looks like the same type of plug/connector on the vest. Is this plug used for accessories or is it for battery charging, or is it for both, or neither??? Thanks in advance.

 

Will work for both .

 

You might want to check under the seat and see if there's a fuse in the line. I have a plug like you describe that I only use for the battery tender so it isn't fused. But if I were going to run something electrical (like heated clothing) off the plug I'd probably want one. Just a thought.

 

You might find two plugs. Typically the rear one is hard-wired to the battery (stock) so you can plug in a battery tender. (output live all the time)
A 2nd plug for a vest is usually switched so you don't drain the battery if you leave the vest plugged in with the bike 'off', like would happen with the rear plug.
The 2nd (front) plug is usually something you'd have added to accomodate the use of a heated vest and hence, they're up front on the frame at the front of the bike's seat where you can get at them easily to plug the vest in.
I have the two plugs, both on the left side of the frame; the front one near the rear cylinder, the other tucked in the frame by the left shock upper mount.

CN