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Battery keeps draining

Tiny
AGUSTINO CAMBALON
  • MEMBER
  • 1998 HYUNDAI STAREX
  • 2.2L
  • 4 CYL
  • 2WD
  • MANUAL
  • 180 MILES
If I disconnect the battery cable for a while; while the engine is running the engine won't stop indicating that the alternator is working, but when I test the battery voltage while engine is running the battery voltage is exactly 12 volts indicating that the alternator is not working. However if I disconnect the battery cable and test the alternator output it indicates 14 volts. What could be the possible problem?
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Monday, September 21st, 2020 AT 11:56 PM

5 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

You never ever disconnect the battery while the engine is running. That tests nothing and can cause damage to the modules. The modules and relays need battery voltage to work and taking away the power will not allow the systems to operate.

The reason it stays running for a little time is the magnets in the alternator are charged and when that charge goes away, it will stop.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

https://www.2carpros.com/articles/car-battery-dead-overnight

You need to start with testing the alternator. I attached a guide for you to follow for testing.

As far as the draining down overnight, I attached another guide for testing for a parasitic draw.

Roy
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Tuesday, September 22nd, 2020 AT 1:05 AM
Tiny
AGUSTINO CAMBALON
  • MEMBER
  • 5 POSTS
  • 1996 HYUNDAI STAREX
  • 2.5L
  • 4 CYL
  • 2WD
  • MANUAL
  • 180 MILES
My battery keeps on draining every time, I tested the battery voltage while the engine is running and it only reads 12 volts, indicating that the alternator is not working. I disconnect the battery cable for a few seconds and the engine continues to run and the voltmeter reads 14 volts. However when reconnect it, it goes to 12 volts.
What could be the possible problem here?

Thank you.
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Wednesday, September 23rd, 2020 AT 4:41 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

I attached a guide for you to follow for checking the charging system.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

It does sound like the alternator is not working at all.

https://www.2carpros.com/articles/how-to-replace-an-alternator

As I stated before, never remove the battery cable while the engine is running as you can damage the modules and it tests nothing.

Roy
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Wednesday, September 23rd, 2020 AT 4:41 PM (Merged)
Tiny
AGUSTINO CAMBALON
  • MEMBER
  • 5 POSTS
Thank you very much Sir.
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Wednesday, September 23rd, 2020 AT 5:35 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You are welcome.

Always glad to help.

Roy
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Thursday, September 24th, 2020 AT 2:31 AM

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