What causes low voltage on an alternator battery?
Check for voltage drops at the positive and negative battery cable connections, the alternator BAT+ power connection and the engine ground strap(s). Poor ground connections are an often-overlooked cause of low charging output and alternator failure.
What should the voltage be in an alternator when idle?
Other possibilities include a failing voltage regulator, or perhaps an alternator pulley that is too small. Check the voltage at the output of the alternator when the engine is idling, it should around 14 V in most cars, maybe a bit lower (13.5 ish) if the battery is fully charged or if the alternator pulley doesn’t allow full output at idle.
What should the voltage be on a bat alternator?
Measure the voltage across the battery and the big bat alternator terminal to alternator case. There are two things that you are looking for. The charging voltage should be between 13.9v to 14.4v. Also the voltage at the battery and the voltage at the alternator should be within 0.5v of each other.
How can I check the voltage of my alternator?
You can test this by connecting a volt meter between the alternator output terminal and the battery positive terminal while the engine is running – be careful to stay away from belts and fans and anything else that can move. Set the meter on the lowest DC voltage scale and check.
Check for voltage drops at the positive and negative battery cable connections, the alternator BAT+ power connection and the engine ground strap(s). Poor ground connections are an often-overlooked cause of low charging output and alternator failure.
Measure the voltage across the battery and the big bat alternator terminal to alternator case. There are two things that you are looking for. The charging voltage should be between 13.9v to 14.4v. Also the voltage at the battery and the voltage at the alternator should be within 0.5v of each other.
What is the voltage of an alternator at idle?
The actual output voltage produced by the alternator will vary depending on temperature and load, and will usually be about 1.5 to 2 volts higher than battery voltage. At idle, most charging systems produce 13.8 to 15.3 volts with no lights or accessories on.
What to do if your alternator has bad ground?
Place the red lead on the positive battery terminal (if possible dig it into the battery post, not the terminal). Place the black lead on the bad post of the alternator. Same thing as above, if the voltage is above 0.5v then examine the positive cabling for problems.