I have made up a relay and fuse system which does the same job but cheaper and easier to fault find.
I use a realy as shown but use these small individual fuse holders which clip together (Halfords) and I can carry a spare, just in case! They can be unclipped and thrown as they are so cheap.

http://i995.photobucket.com/albums/a...enmods0001.jpg

Clipped together

http://i995.photobucket.com/albums/a...enmods0003.jpg

Tucked in to the cavity for the tools

http://i995.photobucket.com/albums/a...enmods0005.jpg

I have also installed this little gizmo from Gammatronix which shows the battery output. If the output is too low it will glow orange, going to red at less than 11V. This does not show charge but battery output. Here it is orange as the ignition is on, hazzards on, heated grips on, head light on and brake on

http://i995.photobucket.com/albums/a...enmods0009.jpg

Here I have started the engine at tickover with the same load and the light is green

http://i995.photobucket.com/albums/a...enmods0011.jpg

I have switched it so that I do not need it on all of the time. It is powered from the fuses as previously shown.
Even with my GPS and heated jacket I have not been able to get it to go orange. This just gives me peace of mind in that it will trigger before the dash lights would show a problem. That's my theory anyway!

updated photo links so they work now.