voltage of alternator <> alt warning light
joscorstjens - 13/1/10 at 12:00 AM
When my engine is idling, the measured voltage in MS is 11.2V, when a get the engine revved up, the alternator warning light goes off and the voltage
reaches 13.6 volt; when the light is not connected, this trick does not work; what is happening?
dave r - 13/1/10 at 06:53 AM
you need the alternator bulb to start the alternator working.
current flowing through the bulb initially excites the alternator windings
Danozeman - 13/1/10 at 07:29 AM
Is it an led warning light? If so you may need something else in the circuit. Either a bulb or resistor.
wilkingj - 13/1/10 at 12:17 PM
quote:
Originally posted by Danozeman
Is it an led warning light? If so you may need something else in the circuit. Either a bulb or resistor.
LED and a resistor will not allow enough current to flow (to excite the windings) thus using a LED is a bad idea.
Use the Std bulb, its designed for the circuit, and is more than just a warning light!!.... as explained by Danozeman.
A LED and a resistor (in series) will not give the same overall resistance as a bulb, and thus not enough current will flow to exicte the windings.
EDIT:
Is it the std alternator for that particular engine, or is it off a different car. If so, then are the pulley sizes correct to make the alternator
turn at the corrent RPM, ie its turning to slowly, and thus not generating sufficient to put the light out.
OR....
Is the alternator Fu**ed?
Just a thought.
[Edited on 13/1/2010 by wilkingj]
joscorstjens - 13/1/10 at 10:51 PM
new alternator but i'll reconnect the bulb
thx!
wilkingj - 14/1/10 at 12:23 PM
quote:
Originally posted by joscorstjens
new alternator but i'll reconnect the bulb
thx!
Remember the bulb goes between the small terminal on the Alternator and the other side goes to (ignition switched) +12V. (ie one side of the bulb is
NOT connected to earth)
The bulb goes out when the small terminal voltage raises up to 12v (ie its charging), thus you have 12v on either side of the bulb and therefore NO
current flow, and the light effectively goes out! Thats why its not just a warning light.
Its a cunningly simple circuit and not what you would normally expect just for a warning light!
EDIT:
This is assuming its not one of those multi wired Japanese Alternators.
[Edited on 14/1/2010 by wilkingj]