Checking alternator
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Instructor
Joined: Sep 2003
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Checking alternator
'95 LT1 Another dumb one.(Car had set for a week after a 1000 mile trip and would not start. Very dead. Only got a clicking sound) How/where do I check my alternator? The battery is only about 6 months old. Do the interior lights go out after a certain amount of time even if the door is 'latched', but not shut tight? I'm letting it set for a week to see if it fails to start again. Any info appreciated
Team Owner
Joined: Mar 2001
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From: Cincinnati, Oh USA
Re: Checking alternator (SJLJ)
You either have unreasonable leakage current being drawn from your battery, or your battery is at the end of its life and cannot hold a charge. Remove the negative cable from the battery and place an ammeter (VOM test meter set to amps) from the battery terminal to the neg cable. After the courtesy lights time out, switch the VOM down to lower full scale amps and measure the leakage current. GM says it should be less than 50 milliamps, my 87 draws 27 ma. To check the battery, charge it up overnight, remove the neg cable and after several hours from disconnecting the charger, measure the battery terminal volts. It should be above 12.9 volts (full charge). Measure the battery each day, the terminal volts should stay close to 12.9 +. 12.0 or lower is considered discharged, so you can tell the state of charge by measuring the voltage. Your alternator is ok if your dash voltmeter reads 14+ volts cold and drops to 13+_engine hot, engine running.
Thread Starter
Instructor
Joined: Sep 2003
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Re: Checking alternator (jfb)
Thanks for the info. My dash voltmeter shows 14.3 after it warms up, running at hiway speed. It doesn't seem to vary much from that figure. It has since I bought it about 4 months ago. I've put about 2000 miles on it since then and this just cropped up. I don't think I left anything on like a dome light etc, but I know nothing is on now, so here hoping. Thanks again
