Might be seen as a dumb question but, Are you sure you're wiring them up correctly? Almost sounds like they're wired backwards.
Installed correctly. Isn't the first pair I've installed. In fact, installed a pair on a 2018 Fat Bob and they work great. I spent 1/2 day at dealership yesterday. They did finally take back the first pair, after testing them they weren't heating up. They were out of the black Kahuna heated grips. They tested the chrome Kahuna and they heated up a lot better than mine. So, the Parts manager is going to order a set of the black ones, test them, and then if they heat up more than the new ones I installed, he said he would swap me out again. So. I have to say, I am pleased they are taking care of the problem. Lone Wolf H-D in Spokane, WA.