A voltmeter
The alternator uses petrol strength while the engine is running to recharge your motorcar battery for the closest bout it starts your vehivle. While garages keep specialized Accoutrement to quickly diagnose a broken alternator, you can diagnose it yourself via assorted tests with a voltmeter. Stuff of your business Testament be to diffenrentiate if discontent with your battery comes from your battery or not. Whether there is a poser within the battery, you'll devoir to set it before you can fully check the alternator.
Instructions
1. Jog the engine for 30 minutes, so the alternator Testament fully charge the battery (whether both are working fly). You can handle the complete day provided that Testament produce the interval pass faster. As with the headlights, radio and AC, the alternator doesn't lose potentiality blameless owing to the engine is running faster.
2. Use the links in Resources to memorize reverse the process with an Epsom salt solution and proper overnight charging with a three-step charger.8. Continue the alternator test if you have a good battery. Start the engine.
This is expressly exceptional in that leaving it in the ammeter income keeps resistence further low and you could short your battery. A voltmeter, by contrast, has elevated resistence, so it won't damage the battery.
4. Remove the explanation from the ignition. Turn off all electrical devices, such as headlights and air conditioning.
5. Establish the metre readout to affectation between 9 and 15 volts.
6. Touch the voltmeter's two metal probe tips to the two battery terminals. Clinch a clear-cut reading by touching murky to opposite and bloodshot to decided. A voltage of less than 12.5 indicates something is definitely mistake, nevertheless doesn't distinguish if it's the battery or the alternator. A voltage of 12.8 or deeper probably means your battery and alternator are both fine, but you'll still need to do a load test to be sure.
7. Test the battery under a modest load. First, insert the ignition key and turn on the hazard lights. Don't start the engine, since a few lights are enough for this test. The battery should still manage around 12 volts. If your reading is lower, then you'll have to end the alternator test right there until you fix the battery or get a new one. According to BatteryStuff.com, 80 percent of battery failures come from the reversible process "sulfation." This is a coating of the internal metal plates with electrolyte. Copper the voltmeter to its direct-current setting; batteries assemble DC capacity, not AC.3. Whether you don't keep a voltmeter, pin money your multimeter to volts, not amps. This converts the multimeter to a voltmeter.
Wait 10 minutes for the battery to recover any charge lost starting the car. Take another volt reading of the battery. Less than 13 volts means the alternator is bad. More than 15.5 volts means the battery isn't properly taking up a charge from the alternator. Instead, the charge is flowing from the alternator right into the voltmeter. Since case, your alternator is fine but your battery isn't.
9. Check for voltage reduction anywhere between the alternator and battery. A reading of more than 0.4 volts between two points along their joining wiring needs resolving--for example, a cleanup of corrosion or dirt, or fixing loose wiring.
10. Test for voltage loss between each battery terminal and its respective cable clamp. White matter builds up there and reduces conductivity. If the voltage drop is greater than 0.1 volts, this is too much for such a short distance. Turn off the ignition, put on some insulating gloves, remove the clamp and chip away at the residue with the end of a screwdriver or a similar implement. Use common sense. Fan the area to clear the air of any explosive battery gas. This could otherwise ignite if the clamp and terminal spark. Such explosions often lead to blindness.
