every time ive tried to use my fairings cigarette lighter port to keep my phone or GPS charged, ive found that it put out little-to now power. ive tried different usb adapters and cables (all of which work fine in my truck), but when plugged into the bike, my phone's charging screen shows an incredibly slow charge, or it says its 'charging' but it still ends up losing battery as i go.

any ideas what the issue could be?

 

Download an app "AMPERE" it will tell you the charge rate.

 

Assuming you are receiving a good 12 volts, you need a "Rapid Charger", putting out a solid 2 amps, AND a known good cable also allowing the solid 2 amps flowing thru it. Many cables reduce it down, so sometimes it can be the cable.
My S7 Edge, when plugged into a solid 2 amp system, shows "Rapid "Charging", if it is less, it won't show that.
Most of today's smart phones and tablets will not charge on one amp with apps running, in fact they will discharge.
One amp chargers and cables make decent power supplies for dash cams, etc, but you need to mark them and keep them away from your 2 amp stash.

 

Have you taken a good look at the cigarette lighter port? Mine was doing what you described on my 2009 and the inside was starting to rust in various places. Replaced it with new one no more issues.

 

On mine it has a 15 amp fuse and runs 10 amps all day.

My heated jacket and gloves draw 9.2 amps and my 15 amp fuse on both bikes has never tripped, even at 22F when they are at the max I will ever use. My IPhone charges at 5 V at 1 amp and my Ipad uses 5V at 2.1 amps. The 2.1 amp charger draws about 5 amps on a 12 volt system. My phone charges faster with the 2.1 amp charger. A USB 2 charges at 0.5 Amps and the 3 at 0.9 amps for comparison. Dedicated charging ports are usually 1.2 to 1.5 amps.

You should be able to draw 10 amps comfortably from your cigarette socket. If not, as someone said earlier, corrosion, rust or poor contacts are robbing your electrons.

added for clarity
Actually, my heated gear runs on a dedicated port, my girlfriends plugs into the lighter as well as using a splitter and charging both phones (dual usb socket) at 1 amp at the same time.

 

I believe that you will likely find your answer there.

 

I replaced the socket in my 2009 with the socket from the HD accessory 12 v port, it's a direct replacement. The inside of the 12v port is different than the lighter. $20, problem solved.

 

You can go cheap

Or powerful

 

am guessing that cig lighter was part of the fairing loooong before most were charging cell phones from cig lighter ports.

It was designed for.....lighting cigarettes! Though it makes me wonder why there's not a bottle opener on the bike too for beer.

 

Mmmmm - a bottle opening USB charging cigarette lighter....