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Old Oct 1, 2015 | 10:50 PM
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Default Battery or Alternator

Long time ago if we wanted to see if the alternator was good or bad, we would get the car running and then disconnect the battery. If the car died, the alternator was deemed bad. If it continued to run, the battery was dead. Is this still a way of testing?
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Old Oct 1, 2015 | 11:17 PM
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Like you said, that was a long time ago but today you can do some damage to the electrical system with this method. Have the parts checked with the proper equipment.

Last edited by Jud Chapin; Oct 2, 2015 at 10:22 AM.
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Old Oct 1, 2015 | 11:26 PM
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Multi-meter is a nice tool to have.
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Old Oct 1, 2015 | 11:30 PM
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Originally Posted by Jud Chapin
Like you said, that was a long time ago but today you can do some damage to the electrical electrical system with this method. Have the parts checked with the proper equipment.


Go to Horror Freight and buy one or borrow a Multi-meter and check the voltage while the car is running. It should be 13.5(low) to 14.+or- volts
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Old Oct 2, 2015 | 09:27 AM
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thats how I do it, easy and simple. not on newer cars though.
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Old Oct 2, 2015 | 10:01 AM
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Yea on any of these cars that's how I would check it. They aren't full of all the sensitive electronics newer cars have on them.
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Old Oct 2, 2015 | 10:22 AM
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Used to do that on generator equipped cars but on an alternator car can cause a voltage spike. Did that in an auto shop class years ago and the alternator shot up to 34 volts.
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Old Oct 2, 2015 | 10:57 AM
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as said, no, not accepted method anymore.

HF has free multi-meters, coupons all over the web and in almost every magazine, so no excuse not to have one (or a dozen ha ha). it will prove invaluable when troubleshooting, battery, alternator, shorts, voltage drops, resistance, etc.
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Old Oct 2, 2015 | 10:59 AM
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Originally Posted by 1Fordman
Used to do that on generator equipped cars but on an alternator car can cause a voltage spike. Did that in an auto shop class years ago and the alternator shot up to 34 volts.
It's just not worth it. A voltage spike can do some serious damage.
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Old Oct 2, 2015 | 05:44 PM
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Voltage spike from a defective, relatively new alternator, a few years ago ultimately lead to me having to replace a/c blower motor and wire from fuse block just this week and a new ecm a year ago.
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Old Oct 2, 2015 | 08:39 PM
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Pull up to a wall at night with headlughts on. Shut jff engine. Headlights get a lil dimmer? You are charging. Headlights get a LOT dimmer? You need a battery...and a jump start!
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Old Oct 4, 2015 | 08:39 PM
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Originally Posted by derekderek
Pull up to a wall at night with headlughts on. Shut jff engine. Headlights get a lil dimmer? You are charging. Headlights get a LOT dimmer? You need a battery...and a jump start!
Interesting. I'll have to try that.

I think the obvious is to use the right tool for the job and now I realize the question was crazy and heat of the moment. Even though it's been a weekly driver, I was surprised to see it not start after sitting for what I consider to be a short time. The last thing I need is to not start at the most inopportune time.
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