Voltage low and battery light comes on at random

[dvtr-]

Trying to figure out what's the issue. Alt or the battery. I'll turn the car on and after a few min the voltage goes from the normal 13-14 to under 12 w the light on and wont fix itself until after I restart the car. Has happened twice already in one week.

 

[specracer]

My test is, when the car is running, pull off the negative battery terminal. If the car stays running, the alternator is charging. Im sure other real mechanics will have better suggestions, but this is what has worked for me.

 

[apex svt]

Old 4.6 trick. Turn the ignition on, hold a wrench to the alternator pulley/nut. If it’s not magnetic, it’s toast.

 

[01yellercobra]

Disconnecting the battery while the engine is running isn't recommended with the newer cars. The arc can kill the ECU.

I'd check all the connections and make sure the grounds are good. Maybe the alternator is starting to go out.

 

[2003RedfireVert]

This has alternator written all over it. Plenty of ways to check and verify. My money is on the alternator.

 

[1FastFord]

certainly, seems like alternator or battery

 

[Bamaterminator]

Went through exact same thing last year. Mine was alternator. Got a kmj no more issues.

 

[hotcobra03]

Pulling neg terminal while running has been my way.

Battery arc happens every time I connect a battery,,

 

[Bullitt1448]

Battery arcs because there is a load on it, lots of things are powered up even though the car is shut off

 

[MG0h3]

Geez guys.

A voltmeter is $20 at any parts store.

You’ll need one at some point anyways…


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