My battery light is on

Tiny
LADYCHEVY79
  • MEMBER
  • 1979 CHEVROLET EL CAMINO
  • V8
  • 2WD
  • AUTOMATIC
  • 650,000 MILES
I have a 1979 El Camino and I just put on a new altanator and the battery light is still on when I take the battery post of when started it dies when having a new altanator does it supose to stay started? What to check for next?
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Tuesday, March 1st, 2011 AT 1:56 PM

3 Replies

Tiny
GARETHSTURMAN
  • MEMBER
Make sure all connections are secure and that the positive and negatives are in the correct places, also a positive from the battery to the alternator is needed, just ensure all connections are properly connected. After that make sure belt is not slipping and it good condition.
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Tuesday, March 1st, 2011 AT 1:59 PM
Tiny
GARETHSTURMAN
  • MEMBER
Another tip is check the battery is in good condition, bad alternators ruin the battery so the new one may not be charging it.
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Tuesday, March 1st, 2011 AT 2:03 PM
Tiny
CARADIODOC
  • EXPERT
DO NOT REMOVE THE BATTERY CABLE while the engine is running! If the generator is working, system voltage can go well over 30 volts and destroy the ignition module and the diodes and voltage regulator inside the generator. On newer cars that can destroy the many computers. Removing the cable was a trick done by mechanics many years ago when they didn't understand how these simple systems work.

Instead, use an inexpensive digital voltmeter to measure battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. Since the battery light is on, we know that turn-on circuit is working. That only leaves the generator / voltage regulator or the output wire between the battery and generator as GarethSturman suggested. If that wire is broken, you will find high voltage on the output terminal on the generator. Another test is to measure the voltage on that output terminal when the engine is not running. You must find full battery voltage there.

To check the belt for proper tightness, try to turn the generator's pulley by pushing on the fan with your thumb. If the pulley spins under the belt it is too loose. Uhm, ... It should be obvious, ... Do that while the engine is not running! :)
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Tuesday, March 1st, 2011 AT 2:45 PM

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