I own a 12 Ultra, and I'm getting ready to upgrade my audio system, and while I was in there, I'm considering replacing the useless air temp gauge with an oil temp gauge in the fairing. Anyone performed this swap? If so, which oil temp gauge works best at the best price? Obviously it's a want not a need, and I could always upgrade the oil dipstick to an oil temp/dipstick. Just thought it would be nice to have it in the cluster up top...........

 

I did it a few years ago on my 06 EG and just used the kit from Harley. It's a nice useful upgrade over the air temp gauge.

 

^^^X2^^^
easy mod and much better info over how warm the air is.

 

I just did that swap. It was kind of a pain in the butt to get that plug out of the oil pan. Finally had to stand on a breaker bar to loosen up the plug. I had already prepped the sensor and the plug adapter to sensor. So when I finally got that plug finger loosened it came out and I shoved a finger in the plug hole. Lost about a teaspoon of oil. I immediately screwed in the prepped sensor and adapter and torqued to specs.

I ran the wire on the inside of the frame and to the outside of the right down tube. I had plenty of wire to reach the gauge. You disconnect the stupid air temp sensor and plug in the oil temp wires where the air temp sensor was connected. Boom done.

 

I did that with my 2003 and swapped out the air temp guage for Oil temp. I now own a 2017 Limited and with the lesser amount of gauges I cannot do any swapping. Only option at this point the oil temp dipstick which I hear is kind of flimsy and you cant readily read anyway. So I use an infrared digital heat gun which I keep in bike. Some of my riding entails riding into downtown NYC so heat temp of a concern. Will see what temps I get with new bike. However I get higher readings in rear of 230 and 210 in front and the cooling heads are like 140. So the heads are nice and cool with the liquid so it obviously works good

 

I used the kit from Harley (the gauge is an exact match to the other ones). It was a pretty simple installation except one thing had me stumped for a few minutes and that was the wire connection from the air sensor, I couldn't find it. Well, I felt a little stupid after I figured out it was the little black box thing attached to the frame in front of the left side of the fuel tank.
To make the wiring from the actual sensor discreet, I cut it, extended it, and then routed it up through the battery compartment and through the tunnel under the fuel tank.

 

Did that a couple years ago on an '07 Ultra. Pretty much as has been described in other replies, except I found removing the fuel gauge made for easier access to the air temp for removal, and installation of oil temp gauge.