Re: 12V warning light

Posted by Kevin (FL) on December 07, 2004 at 11:59:57 from (12.77.199.222):

In Reply to: 12V warning light posted by Bubba on December 07, 2004 at 11:31:38:

Bubba,

The light is connected on one side to the field current system inside the alternator and to a switched (12v) side of the ignition. When you turn the key on but have not started the tractor, the field acts as a ground and power flows through the light and then to ground - this lights the bulb. Once you start the tractor, the voltage at the field is powered internally by the output of the alternator. If this value is exactly the same as the battery voltage, then you have the same voltage on each side of the indicator light. If the alternator is charging, the light stays off. If the output of the alternator should drop, there will be less voltage on the field side of the light and more voltage on the switched ignition side of the light. The result is that some amount of electricity will flow through the light and into the field and the light will glow proportional to that voltage difference. Some of the delco alternators also use a resistor in parallel to the indicator light. Hope that helps. I found a good website awhile back about this subject but don't have the address handy.

Follow Ups:

• Re: 12V warning light little john 12:05:38 12/07/04 (2)
  • Re: 12V warning light gusc 14:59:53 12/07/04 (0)
  • Re: 12V warning light Kevin (FL) 12:17:39 12/07/04 (0)

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