How to lower voltage

nicknick109

I have a Garmin Streetpilot i3 fitted to my motorcycle.Problem when stationary with engine ticking over works ok when I drive away it goes off. Stop and turn it on and it works again drive away and it goes off again.
Not sure if there is a protection thermo/couple fitting and my alternator is sending too much voltage.
i3 needs 3w/13.5 volts and I am sure my alternator is producing 14v + (bike is a diesel fitted with a Hatz stationary engine)
So assuming I need to fit a resistor in line somewhere could anyone advise what size to drop say 1 volt and where would it fit on the + side or -
Thanks any help.
Nick

fwor

While not impossible, it would be most unusual for a GPS that's intended for in-car use to turn off if the voltage rises a bit. It's quite common for a car's 'nominal' 12V to be 14+V - the GPS should have an internal regulator to guard against over-voltage.

IMO it's more likely to be vibration-related, or - possibly - excessive electrical noise if there's something wrong with the bike's alternator or regulator.

If you're ~sure~ that the problem really is over-voltage then fitting a resistor probably won't be the best solution - a 12V regulator would be better.

spud17

I am sure my alternator is producing 14v +

This morning I fitted a new battery to an Escort.
When someone tells me they need a new battery, I always check the alternator output.
While not a complete test I expect to see around 14v at1000rpm, this one was 14.2v, the sat nav was fine.

bike is a diesel fitted with a Hatz stationary engine)

If it's the same Hatz that we have in our plate compactors (something like 1B20), then these are pretty crude.
My guess would be that the voltage control is not fine enough for your needs.

espresso

Sounds a bit of a unique beast this motorcycle! You can't really use a resistor to drop the volts and you are probably getting spikes that are causing your problem. You could try using a voltage regulator circuit e.g here