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hushcar
Samba Member
Joined: November 05, 2005
Posts: 63
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 Posted: Sat Mar 28, 2015 4:54 pm Post subject: alternator idiot light (blue wire) |
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| Trying to remember how the light in the dash is wired to excite the alternator. First my alternator has an internal regulator so I know the blue wire runs up to the dash light. I believe the alternator needs 12 volts to the blue wire to get it to charge. So when the key is turned on how does the dash light come on? Does 12 volts go to one side of the bulb and is the bulb grounded to make it light? Is 12 volts still going to the alternator in the running position? Thanks for any help. I'm starting with just wires here and an aftermarket fuse box |
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
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kreemoweet
Samba Member
Joined: March 13, 2008
Posts: 3898
Location: Seattle, WA
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| Posted: Sat Mar 28, 2015 6:47 pm Post subject: |
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The alt/gen warning lite gets sent "12" volts from the ignition switch,
via the tab on the bulb holder that contacts the isolated base plate.
The blue wire connects to the 1/8"connector on the bulb holder, and
runs back to the D+ terminal on the alternator. The D+ terminal is
grounded when the alt isn't spinning, so the bulb lites up. When the
engine is started and the alt starts putting out voltage, then the
battery voltage is the same as the alt voltage and the D+ voltage
should also be the same, so there is no current through the
warning light and it goes dark.
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