VOLTAGE Problems.......
Thread Starter
Pro
Joined: Dec 2006
Posts: 678
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VOLTAGE Problems.......
The alternator on my 93 blew apart last week (chunks of metal all over). I drove about 50 miles in the desert to get to a shop. It has since been replaced by a new Alt. Now my voltage drops when the car is stopped and in gear with the A/C, headlights and radio on. When my turn signal is on it flashes really slow and dims my gauge lights. Sometimes "SYS" flashes by the speedo and "SECURITY" also flashes at the same time. Any ideas? Thanks
Thread Starter
Pro
Joined: Dec 2006
Posts: 678
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It sits at 13.9 - 14.3 Volts during the day with A/C on and moving. At night with A/C, radio and headlights/turnsignals it sits at 11.8 - 12.8 Volts with a very slow signal and dim dash lights. It was replaced at a Corvette only shop.
Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
It is more important to know what the battery reads with the key on. I would expect it to read what it does when running with a new alternator but if the battery is toast you will get sys light. Turn the key on and look at the volts if it is less than 12.1V you probably need a new battery.
Racer
Joined: Aug 2005
Posts: 252
Likes: 2
From: lancaster pa
It is more important to know what the battery reads with the key on. I would expect it to read what it does when running with a new alternator but if the battery is toast you will get sys light. Turn the key on and look at the volts if it is less than 12.1V you probably need a new battery.
The old alt. may have fried the battery just before it
took a dump
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Don't bother with the dash voltmeter reading when the engine is not running, it is in error with the engine off! The alternator should be able to hold up the electrical load, that is, the dash voltmeter should read about 14.3 volts cold and 13.3 volts hot. If the alternator is not charging the battery, the red battery symbol will light on the dash. The alternator cannot put out rated current at idle and if you have unusually low idle rpm (below 700 rpm), or if someone put a larger pulley on the alternator, or a smaller crank pulley to reduce the parasitic load for more hp, then your battery will supply the car electrical load at idle and you will see low voltage. The battery is considered discharged at 12.0 volts and below and it should be charged up at least overnight with a battery charger. You can tell the state of charge in your battery by measuring the voltage at the battery terminals with a voltmeter while under no load. 12.0 volts and below, discharged. 12.9 volts and above, fully charged and linear in between. I don't believe your electrical load is excessive.
Your dash voltmeter should never show below 13 volts if idle rpm is 700 or more rpm and you have OEM pulleys! If below 13 volts, then you have a defective alternator.
Your dash voltmeter should never show below 13 volts if idle rpm is 700 or more rpm and you have OEM pulleys! If below 13 volts, then you have a defective alternator.
Last edited by jfb; Jul 21, 2008 at 10:06 PM.
