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Discussion Starter · #1 ·
At the risk of sounding stupid, what kind of tester would I need to test my alternators output. I don't want to spend a lot of money on a tester, but would like to make sure that my alternator is putting out enough juice. Thanks, Greg
 

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A basic volt meter will tell you if its charging at all. Measure at the battery, engine off 12 to 13 volts, running 14.5 to 15 volts. (If the battery measures less than 12V in the OFF condition [Neg cable removed], it probably has a dead or open cell, even a "dead" battery will measure near 12V with no load) This won't tell you if it has enough capacity though. The only way to measure this is with a load tester that can simulate a load (lights, motors, etc) on the output. AutoZone and others will normally load test your electrical system free and they have the specs on the Amp rating for each car.
 

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Ditto
 

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With the engine running at about 1000 rpm's, take a voltmeter and connect to the actual battery terminals.

You should have AT LEAST 13.8 volts. 14.5 is what I would consider MAX. 15 is too high. The ideal charging voltage is 14.2 volts.

Keep the meter connected and start turning on accessories, headlights, radio, turnsignal, heater/A/C blower, etc. You should not see a major drop in voltage (like 12.9 for example).

This would indicate proper charging.
 

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Discussion Starter · #5 ·
If I see a significant drop in volts when I turn on acessories, Like fuel pump, I would need a " bigger" alternator right?
 

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Greg,
You can yank the thing off and take it to
an autoparts that has a tester. It spins it the correct rpm and puts a load on it to check for output. If its no good, youll be right there to get another one. Most NAPAs
have the tester.
 

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And if you buy a VOM, buy a digital one, not an analog one. Either will work here, but some auto electrical stuff doesnt like the analog.

FWIW Greg, I had mine tested at a Carquest store and we found some connections not quite kosher. VERY cheap fix. Theres a $10 device that takes the wires out of the plastic connectors allowing you to clean them up mint. Highly recommended procedure if you;re dealing with an orignal harness.

[This message has been edited by 427L88 (edited 02-23-2001).]
 
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