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post #1 of (permalink) Old 09-08-2003, 06:19 PM Thread Starter
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Alternator or voltage regulator?

Is there a simple way to tell if the voltage regulator is bad w/o replacing it? The jeep is not charging anymore. The alternator and voltage regulator are both the same age, about 6 months.

Also, is it normal for a starter to smoke and smell like an electrical fire if you crank the hell out of it w/ a half dead battery?
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post #2 of (permalink) Old 09-09-2003, 08:07 PM
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Re: Alternator or voltage regulator?

Take off the altinator and take it to Auto Zone or similar parts house. They will test it for free.

As for your starter....NO. It should not smell. Sounds like you have electrical problems.

A little suggestion. When you get over 20 years in age (the jeep that is), wiring problems start...it is usually a combination of old cracked insulation and corroded connectors. Two solutions...clean and/or replace as you come across a bad circuit or buy a new harness from Painless wiring.
post #3 of (permalink) Old 09-10-2003, 09:25 AM
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Re: Alternator or voltage regulator?

Actually, if you "crank the hell out of it w/ a half dead battery" you're commiting starter abuse. Abuse it severly enough and it would be normal for it to overheat, smoke and smell bad.

The real question now is whether it's been permanently damaged. Time will tell.
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post #4 of (permalink) Old 09-10-2003, 11:58 AM
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Re: Alternator or voltage regulator?

Cranking with a low battery causes the starter to draw excessive current, the armature isn't breaking connection fast enough. Death to a starter eventually. (You'd think it draws less current with lower voltage according to Ohm's law, but remember the commutator interrupts the current, so the interruption isn't as fast. Each segment has a chance to overheat.)

The alternator regulator tests -
If it's got an external regulator - disconnect the field wire at the alternator. Temporarily touch a jumper lead to the alternator's field terminal, the other end to (+) battery. If it charges, alternator's OK, regulator or wiring is bad.

If it's an internally regulated alternator - look on the back for a hole about 5/16" diameter shaped like the letter "D."
Insert a small metal object, like an Allen wrench or short pocket screwdriver into the hole while running (if you have the right hole there aren't any rotating parts to hit - be sure it's the "D".) Reach in abot 1/2" till you feel something, then angle the Allen wrench so it grounds to the case. If it charges then, regulator's dust, alternator's OK. You are bypassing the regulator just like you did above.
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post #5 of (permalink) Old 09-10-2003, 05:11 PM
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Re: Alternator or voltage regulator?

</font><blockquote><font class="small">In reply to:</font><hr />
Cranking with a low battery causes the starter to draw excessive current, the armature isn't breaking connection fast enough. Death to a starter eventually. (You'd think it draws less current with lower voltage according to Ohm's law, but remember the commutator interrupts the current, so the interruption isn't as fast. Each segment has a chance to overheat.)

[/ QUOTE ]
Er, … not exactly, look up something called back EMF for the explanation.
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post #6 of (permalink) Old 09-10-2003, 08:53 PM
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Re: Alternator or voltage regulator?

Taz - true - Back EMF -- but that's lower due to the slower rotation and commutator interruption - right?

He He - I didn't want to get that technical, wanted to stay away from inductive reactance, pulsating DC etc, but you can.
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post #7 of (permalink) Old 09-10-2003, 09:34 PM
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Re: Alternator or voltage regulator?

Basically, the winding connected to the brushes has to move fast enough through the magnetic field to create sufficient back EMF. If not, excessive current flows in the winding causing the high heat.
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post #8 of (permalink) Old 09-10-2003, 10:19 PM Thread Starter
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Re: Alternator or voltage regulator?

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