20-01-17, 12:13 PM
I agree that a switchgear or wiring problem must be causing the mysterious issue with main beam coming on of its own accord, hopefully changing the l/h cluster will sort that.
Even if there was a short in the switchgear that meant the high beam was on without you noticing, the alternator ought to cope OK even with the spots and heated grips. A short to ground should blow a fuse.
Are you sure you've not been sold 100W bulbs? If that's not the cause then I'd guess the alternator or reg/rectifier are faulty and not supplying enough current. If the battery's been killed a couple of times it may not be as healthy as it should be… these modern high CCA ones are a bit less robust in that respect.