Re: Why Pos Ground

Posted by Bob on August 11, 2005 at 07:57:45 from (64.21.249.40):

In Reply to: Re: Why Pos Ground posted by JT on August 11, 2005 at 07:43:37:

JT,

Your observation is correct only part of the time!

DC motors, with WOUND FIELDS, such as conventional starter motors, DO NOT reverse when the battery polarity is reversed.

That is why you can change a tractor or old car from (+) ground, over to (-) ground, the starter will operate correctly. Also, older motors, such as older heater and fan motors will not reverse with a polarity reversal.

What you have observed is small-engine starter motors that have a PERMANENT MAGNET FIELD. They will reverse when their power supply polarity is reversed. Also, most NEWER heater fan motors are permanent magnet field units, and will reverse when the power supply polarity is changed.

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• Re: Why Pos Ground JT 08:08:46 08/11/05 (0)

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