How many volts does an alternator need to be?
How many volts does an alternator need to be?
A car alternator needs to be putting out at least 13-14 volts (ideally between 13.8 and 14.2 volts) to effectively charge a 12 volt car battery. If the alternator is putting out too much voltage (15+ volts), it is likely your battery acid will boil over out of the battery.
What to do if your alternator is over charging the battery?
Ask an assistant to start the engine and hold engine speed at about 1500 RPM. Measure voltage across the battery with your DMM. You should get 0.5 to 2 volts higher than base voltage. If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty.
How can I tell if I have an alternator problem?
To differentiate an alternator problem from the battery, you will need to use a voltmeter to check for voltage. First, turn off the engine and check the battery voltage. A fully charged battery should have a reading of 12.65 volts. Next, turn on the engine and recheck the voltage. You should have a reading of 13.5 to 14.5 volts.
What happens when the voltage of an alternator drops?
Voltage drops on the negative side can cause overcharging. When a new alternator is installed, check the battery voltage and use a battery charger to bring the battery up to full charge before you return the vehicle to your customer. Also, start the engine and use your DVOM to check the charging output of the alternator.
What should the voltage be on an alternator?
Alternator Testing: What Is The Correct Voltage? For some alternators, it’s normal to see as low as 13 volts. For some, a constant 13.6 volts is an indication of a problem.
What causes an alternator to over charge a battery?
Measure voltage across the battery with your DMM. You should get 0.5 to 2 volts higher than base voltage. If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty. Other potential problems are a faulty voltage regulator or a problem in the charging system wiring.
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.
When does the alternator light turn on the battery?
On older vehicles, the battery light would turn on the alternator light when the alternator output or battery voltage dropped below a preset value. The battery light on modern vehicles, however, is controlled by data and trouble codes. This is why a scan tool is essential to diagnosing a charging system.
What does it mean when battery and alternator don’t match?
Also the voltage at the battery and the voltage at the alternator should be within 0.5v of each other. If the voltage at the battery and alternator don’t match. For example the battery reads 12v and alternator reads 14v. This means that there is an issue with wiring. While applying the same conditions as above.
What causes an alternator to put out low voltage?
Likewise, what causes an alternator to put out low voltage? Poor ground connections are an often-overlooked cause of low charging output and alternator failure. Voltage drops on the positive side of the charging circuit can cause undercharging. Voltage drops on the negative side can cause overcharging.
On older vehicles, the battery light would turn on the alternator light when the alternator output or battery voltage dropped below a preset value. The battery light on modern vehicles, however, is controlled by data and trouble codes. This is why a scan tool is essential to diagnosing a charging system.
How many volts should an alternator be putting out?
How many volts should an alternator be putting out? Most automotive batteries are lead acid 12-volt DC (Direct Current). Each of the six cells in a 12-volt DC battery produces 2 to 2.1 volts. When the engine is running, the alternator will typically put out between 13.8 to 14.8 volts.
What does it mean when your alternator is not working?
Most vehicles have a specific light that is battery shaped that will come on to signal if there is an issue. Some may even say ALT. Alternators often have outputs between 13 and 15 volts. If it’s not working correctly the voltage can go below or above these levels, which will signal the warning light.
