Hi guys Just changed the battery on my bus as the battery was flat I have put on a new battery and the battery warning light will not go out even after a long drive Any advice appreciated
..and if it's charging.. have you knocked the blue wire off the regulator that goes to the front and tells the light on the dash to go out?.. Sent from my SM-G930F using Tapatalk
Or, the same if the bulb has died, tho I haven't tried this myself, no bulb, no exciting! Clearly, not in this case, but worth considering if the bulb doesn't come on initially.
Ah!.. I though the blue only became 'live when the alternator generated... so it's live from ignition also? and 'cancelled out' once it starts charging.?.. Now I'm not sure how my fuel pump relay works . Sent from my SM-G930F using Tapatalk
One side of the bulb is connected to battery +12V. The alt light output is grounded (effectively) when the alt isn’t providing power (ie engine not running). When it is, the alt light output goes up to +12V, so the bulb has 12V on both sides of it, so goes out. As Zed said, it also provides a small excitation current to the regulator, so the alt does actually fire up.
So if the blue line is live 12v via the dash light grounded at the regulator until its balanced by 12v via the alternator my pump solenoid should get activated when the ignition is on and as its grounded let both currents flow through the solenoid activation circuit when engine running and continue to activate it .. but then as current could flow either way to it, would the dash light come on again? Sent from my SM-T580 using Tapatalk
Not really clear how you've got stuff wired. Pic? The alt light tab on the alternator will effectively be at 0V when the alt's not running. It will have (a rather lumpy) 12V on it when the alternator's producing power (ie engine running), so that could be used to switch a relay. I'd be careful what you connect to it: it's driven from the three small aux diodes in the diode pack, and these could go pop if you've got weird stuff connected. Grounding the alt light output when the engine is running for example will likely destroy them.
The idea is that the light bulb in the dash will let through a max 0.1 A as its 1.2watts The regulator will try to power up the alternators field control winding from that supply so the voltage at the alternator end will be quite low, not enough you hope to close a 12 volt relay. So no fuel pumping. Once the alternator spins, with that small current flowing in the field winding, the voltage on the alternator warning terminal goes up and the alternator excites. Check the voltage on the relay with the ignition on and the engine stopped, then with the engine running. It should be a few volts max when stopped and about the same as the battery voltage with the engine running If your regulator is not connected to that wire or the diodes are blown, the light never comes on, and the battery wont charge. But there might end up enough voltage on the relay fed back through the bulb for the light to glow dimly and the relay closes giving you fuel pump power as soon as ignition is on, rather than only when the engine runs and the alternator produces 12 volts. The diodes that feed that terminal are pennies to buy, just getting at them is either engine out or levering up the fan housing with thermostat disconnected and carburettor and inlet manifold removed to release the alternator and fan... a faff .
