Yeah, I figure all the "10A fuse" means is that the load draws close to or over 5A
Right, soo....
Flat battery while on holiday (possible ignition left on, or the Innovv not shutting down properly) but battery seeming OK (and replaced)
Slight flicker on neutral light (engine off, bike still?)
LED brake/tail lights acting weird (engine off)
Horn not working while engine off
Everything above working fine when the engine's running.
Spikes in speed on trip logs (presumably while the engine's running...?) Is this new, or just 'newly noticed'? 12V power shouldn't affect the Zumo, assuming it still has its internal battery in reasonable condition? What's this wired to?
You know what you're doing with a multimeter, so I'll assume the battery, charging system etc are all fine
If I've interpreted correctly, all the accessories (inc Zumo and Innovv) are powered straight from the battery, via a relay, which is switched using one of the 'quartet harness' switched live lines? (Which one? The 'accessory' switched live? Or there's a White/Green switched live on the bike side connector that only switches with ignition)
The neutral lamp is an LED, and it's series resistor is presumable selected to ensure long life (I don't have the specs of the LED used, but the resistor value is quite high, I think I measured <15mA last time I was in there). This means that the LED will be close to the 'knee' in its operating region, so small changes in voltage will be noticeable as small changes in light output (if the series resistor was smaller, and the current higher, the LED would be brighter, and in a flatter part of its curve, so the changes in brightness would be tiny and not noticeable). The strange thing is the 'flicker' - if the bike's just sat there, engine off, battery voltage should be falling quite slowly, not moving around much. A loose connector could obviously cause a flicker, but if the bike's sat still... Only other thing is something plugged in that's drawing power, and that power draw changing (resulting in a changing voltage drop, and a changing voltage at the neutral LED). The Zumo
could cause that
maybe, as could the Innovv, or maybe heated grips if they're cycling. Is the flicker regular, or random? Does unplugging the Zumo or Innovv 'fix' it? For an accessory wired direct to the battery to cause a flicker at the neutral LED would require quite some power draw I'd expect... Unlikely to be able to measure the changing voltage with a multimeter - digital too slow, analogue not sensitive enough. Don't suppose you have an oscilloscope?
LED brake/tail: I assume you have an LED strip or bulb or similar wired to the running light via a resistor to drop the voltage and brightness, plus another feed from the 'brake' line through a diode, bypassing the resistor?
Are the stock bulbs still filament, or LED? I must admit, if this is how they're wired, the only reason I can think for them to switch off when you apply the brake is if the additional load of the stock brake light bulbs pulls both 'brake' and 'running' voltages low enough that the LEDs don't illuminate (and with the engine running, voltage is high enough) but this is clutching at straws really... Or the diode has failed short circuit, but this should be fairly obvious
Horn: These are quite voltage sensitive (you have the stock 'pancake' horn?). Each one is a little different, but the ones I have here stop working at somewhere between 9 and 11V. They need enough 'oomphf' to push the coil far enough to start oscillating, once they're sounding the voltage can drop quite a bit lower before they die.
The Horn and brake lights are both powered from fuse C (via the main stop relay) on a White/Green wire, which also goes to one of the connections on the quartet harness connector. (There are two White/Greens on the quartet connector (assuming my diagram is correct)?! The other is powered by fuse J - battery clock backup, permanent live)
Hmm. Both fuses C and J (plus a few others) are powered from the battery via main fuse B (65A fusible link), and also direct from the alternator. Could main fuse B have a poor connection, dropping voltage from the battery until the engine starts and the alternator takes over? If it's blown completely, the bike would be dead (fuse L - FI, coils, fuel pump).
Are you able to measure the voltage on that White/Green line (to battery negative) with the bike off (should be 0V), on (should be battery voltage), on with brake lamps illuminated, and then engine running? Ideally also the same at the battery terminals too, but hopefully by this point you'll have spotted something...