Alternator or battery?

[chevvchelios1993]

Hello and sorry if this is in the wrong category.

My car broke down yesterday, started experiencing electrical failure such as loss of power steering, radio turning off etc. The battery light kept coming on but I noticed when the car was above 4000rpm the light would go off.

Took the battery back and charged it for at least 3 to 4 hours. When I put it back into the car and started it the car I just managed to get home but then died straight away again.

Does this sound more like the alternator or battery do you think?

Thank you

[siwil1]

Sounds more like the Alternator but without getting a meter on it you will never know.

[deggles]

Sounds like the alternator. The 'battery' light will come on when charging voltage dips below a certain threshold. Do you have a multimeter? You should see ~14V across the battery terminals when the engine is running, regardless of rpm.

Note you can usually repair/replace the voltage regulator on the alternator cheaply, rather than replace the whole thing.

[jet_noise]

You need a voltmeter. Not unambiguous as a tool but can help.

[chevvchelios1993]

In response to the above, I don't have a multimeter but my 12v USB socket has a voltmeter.

It usually says 13 - 14 but when I started having the issues it was on 11.5 before gradually dropping to like 0.9 before it starts dying.

In case this helps with diagnostics?

[AlexIT]

chevvchelios1993 said:

In response to the above, I don't have a multimeter but my 12v USB socket has a voltmeter.

It usually says 13 - 14 but when I started having the issues it was on 11.5 before gradually dropping to like 0.9 before it starts dying.

In case this helps with diagnostics?

What does it say when the engine is running?
If it's below 13,7, then most probably the alternator is not charging, if on the other hand it's higher when the engine's running, but once stopped it drops then the battery's dead.

[steveo3002]

grab a cheap meter you can get them for a fiver or so , saves guessing at expensive parts

does point towards the alternator though as if it was working then the car ought that kept going after charging the battery

[chevvchelios1993]

AlexIT said:

chevvchelios1993 said:

In response to the above, I don't have a multimeter but my 12v USB socket has a voltmeter.

It usually says 13 - 14 but when I started having the issues it was on 11.5 before gradually dropping to like 0.9 before it starts dying.

In case this helps with diagnostics?

What does it say when the engine is running?
If it's below 13,7, then most probably the alternator is not charging, if on the other hand it's higher when the engine's running, but once stopped it drops then the battery's dead.

Yeah it's way below, like 11.5 or something

[chevvchelios1993]

Looking like the alternator then, happy Christmas to me

[AlexIT]

chevvchelios1993 said:

Looking like the alternator then, happy Christmas to me

Note deggles' post:

deggles said:

Note you can usually repair/replace the voltage regulator on the alternator cheaply, rather than replace the whole thing.

It could save you a lot of money

[jet_noise]

AlexIT said:

chevvchelios1993 said:

In response to the above, I don't have a multimeter but my 12v USB socket has a voltmeter.

It usually says 13 - 14 but when I started having the issues it was on 11.5 before gradually dropping to like 0.9 before it starts dying.

In case this helps with diagnostics?

What does it say when the engine is running?
If it's below 13,7, then most probably the alternator is not charging, if on the other hand it's higher when the engine's running, but once stopped it drops then the battery's dead.

What he said ^^^^^^^

[chevvchelios1993]

jet_noise said:

AlexIT said:

chevvchelios1993 said:

In response to the above, I don't have a multimeter but my 12v USB socket has a voltmeter.

It usually says 13 - 14 but when I started having the issues it was on 11.5 before gradually dropping to like 0.9 before it starts dying.

In case this helps with diagnostics?

What does it say when the engine is running?
If it's below 13,7, then most probably the alternator is not charging, if on the other hand it's higher when the engine's running, but once stopped it drops then the battery's dead.

What he said ^^^^^^^

It's higher when the engine is running and the car is driving yeah, if you rev the car to like 3 or 4000rpm it won't die, if you let it idle it will eventually die

[jet_noise]

chevvchelios1993 said:

It's higher when the engine is running and the car is driving yeah, if you rev the car to like 3 or 4000rpm it won't die, if you let it idle it will eventually die

You shouldn't need those revs to get the volts. A healthy system will provide some even at idle.