I have a single LED charge monitor. In normal riding it is solid green, when you leave the bike it will eventually switch to blinking green, then blinking orange as the batt voltage drops.
At the other end it will flash green/red (alternating) if overcharging.
When I first start the bike - solid green - no problem. When I start riding for the first mile I get a flashing green/red indicating overcharging. Since I'm a worrier, before the next ride I hooked up a multimeter and when I get the flashing green/red it is 14.7v. The Suzuki (gen3) charging spec is quite wide: 14 -15.5V so my monitor is giving an erroneous indication.
After the first mile the over voltage indication goes away and never reappears until the next cold start which destroyed my only theory. I thought that the initial start made the charging system work harder having just started the bike. However, if my first ride is to the petrol station (< 1 mile away), starting up there does not give me an over charging error.
I am reasonably confident that the bike is not overcharging (new battery btw and it did on old batt too) but I cannot think why it should only do it from cold.
My left field theory is maybe I have corrosion on a connector and the temp change is affecting its resistance but as theories go it's "out there".
I need warmer weather before I start diving in but I may order a new reg/rec since I have more money than sense or, as I'd like to think, I'm being prepared. The Electrex RR851 seems a likely candidate.
I suppose a more rational (cheaper) approach would be to dump the monitor and forget about it
