 puzzling alternator problem |
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| jaybird840 |
  Dec 27 2007, 05:14 PM
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#1
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Member  Group: Members Posts: 163 Joined: 27-September 06 From: Austin, TX Member No.: 6,927 Region Association: Southwest Region  |
Trying to figure out a charging system issue I'm having. My alternator doesn't appear to be putting out any juice... 12.7 volts by multimeter coming from the battery with no key on. 12.5 volts with car running. Idiot light on the alternator appears to be working. If the idle drops under about 400 rpm, my gen light will come on (making me think the light's working as designed, I guess). Voltage meter in the console shows a flat 12v while running (drops to 10v with headlamps lit). All that said, is the voltage regulator internal or external on 'teeers ('75 1.8). If it's external, how can I test it. Best course of action??? Thanks all!!!
--jaybird (IMG:style_emoticons/default/headbang.gif) |
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Replies(1 - 4)
| dr914@autoatlanta.com |
Dec 27 2007, 06:02 PM
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#2
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914 Guru Group: Members Posts: 7,900 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
QUOTE(jaybird840 @ Dec 27 2007, 04:14 PM)  Trying to figure out a charging system issue I'm having. My alternator doesn't appear to be putting out any juice... 12.7 volts by multimeter coming from the battery with no key on. 12.5 volts with car running. Idiot light on the alternator appears to be working. If the idle drops under about 400 rpm, my gen light will come on (making me think the light's working as designed, I guess). Voltage meter in the console shows a flat 12v while running (drops to 10v with headlamps lit). All that said, is the voltage regulator internal or external on 'teeers ('75 1.8). If it's external, how can I test it. Best course of action??? Thanks all!!! --jaybird (IMG:style_emoticons/default/headbang.gif) the quickest check is to replace the external voltage regulator on the relay board and clean the ground at the right firewall from the battery and the rear trans ground strap and recheck. (also make sure the battery terminals and posts are clean |
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| davep |
Dec 27 2007, 06:49 PM
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#3
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914 Historian Group: Benefactors Posts: 5,159 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada  |
I agree with George.
Never trust the console voltmeter, only a voltmeter attached to the battery posts. Also test the voltage from the negative post to the fan shroud on the engine. There should be very little voltage (drop) on the ground circuit. If there is, try a heavy ground strap between the ground on the wall and the fan shroud, thus bypassing the body and the transmission ground strap entirely. The alternator is grounded to the fan shroud. |
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| jaybird840 |
Dec 27 2007, 09:14 PM
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#4
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Member Group: Members Posts: 163 Joined: 27-September 06 From: Austin, TX Member No.: 6,927 Region Association: Southwest Region |
QUOTE the quickest check is to replace the external voltage regulator on the relay board and clean the ground at the right firewall from the battery and the rear trans ground strap and recheck. (also make sure the battery terminals and posts are clean Is it possible to test the voltage regulator (like, with a multimeter) so I don't end up purchasing one to swap and then not need it? (serious personal pet peeve). thanks for the advice!!!!!!!!! |
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| draperjojo |
Dec 27 2007, 09:40 PM
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#5
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sixstrings Group: Members Posts: 411 Joined: 26-December 05 From: Salt Lake City Utah Member No.: 5,317 |
Yeah, you should read about 12.5 volts at the battery with a Digital Multi Meter. Then fire up the engine and it should read 13.8-14.5 DCV. The factory gauges are only good for a reference point.
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