What would cause voltage drop on alternator ,when first startede the output of the new alt. is 14.40 as car runs voltage drops steadily I have installed 3 new alt.

Asked by Harold on 07/26/2013 2  Answers

ManualsOnline posted an answer 11 years, 4 months ago

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5 14.4 volts or even higher is normal for an alternator. If the voltage drops, it means the regulator thinks the battery is fully charged. If the battery is not fully charged, then there must be a high resistance between the alternator circuit and the battery, so it's tricking the regulator into thinking the battery is fully charged. I have found on other cars that corrosion in the cables that connect to the battery can cause this problem. I found one once where corrosion had progressed up the positive battery cable about 6 inches, and the cable wouldn't provide much current flow through the remaining few wire strands. I would do an ohmeter check of the heavy wires connected to the battery, and make sure that the end connections are also clean and secure. Also, there are some aftermarket battery cables that have a clamp at the battery where the wire is clamped to the battery terminal connector, and these are notorious for causing poor connection. Good Luck!
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0 14.4 volts or even higher is normal for an alternator. If the voltage drops, it means the regulator thinks the battery is fully charged. If the battery is not fully charged, then there must be a high resistance between the alternator circuit and the battery, so it's tricking the regulator into thinking the battery is fully charged. I have found on other cars that corrosion in the cables that connect to the battery can cause this problem. I found one once where corrosion had progressed up the positive battery cable about 6 inches, and the cable wouldn't provide much current flow through the remaining few wire strands. I would do an ohmeter. There is a possible drain on your electrical system. Most of the time is something simple like bulb or it can be something more complicated. check of the heavy wires connected to the battery, and make sure that the end connections are also clean and secure. Also, there are some aftermarket battery cables that have a clamp at the battery where the wire is clamped to the battery terminal connector, and these are notorious for causing poor connection. Good Luck!
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