ADVrider - Grip Heater Fuse Blowing

I have these:

http://www.aerostich.com/media/catal.../6/1600_1a.jpg

http://www.aerostich.com/arctic-grip-heaters.html

Installed on my KLR650 and my VFR800 via relays. I've never had issues on the VFR and use a 5 amp fuse (I think).

I installed them on the KLR with a 5 amp fuse and was fine for months, but now whenever I switch from off to high or low with power on, the fuse blows. I went up to a 10 amp fuse and still the same issue. As long as I don't toggle the switch while the bike is powered, I'm fine...so I have to choose my setting before starting the bike. I forgot yesterday and blew the fuse and had to ride home with chilly wittle fingers :(

Any ideas?