Can an alternator test bad but still be good?
If you have a newer battery but your car won’t start, you may have a bad alternator. If you’re tempted to test an alternator by disconnecting the negative battery cable, don’t do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test.
What should a good alternator test at?
If the alternator is working well, your multi-meter should read somewhere in the vicinity of 14 volts (typically 13.8-14.2). If it is reading excessively higher than 14 volts (greater than 15 volts) it is possible that the voltage regulator on your alternator is faulty or going bad.
Can you bench test an alternator?
Alternators have one of the highest return rates of any repair part – often because of misdiagnosis. Bench testing an alternator on a test stand should verify whether or not its output is within specifications. If the unit tests bad, your customer needs a replacement alternator.
Can a car battery be bad but test good?
As long as battery voltage remains above 9.6 volts, the battery is considered “good.” But if it drops below 9.6 volts by the end of the test, the battery may be “bad,” or the battery may have to be recharged and retested if it was not fully charged prior to the test.
Can I test an alternator with a drill?
Be careful if your using a drill to test an alternator, make sure the alternator is securely fixed down and hold on really tight to the drill because when it comes “on load” it will probably try to spin the drill out of your hand.
Can you test an alternator without negative battery?
If you’re tempted to test an alternator by disconnecting the negative battery cable, don’t do it. A good alternator may indeed keep the engine running without the negative cable, but this was never a good test. In the pre-computer days, you could pull it off without damaging anything.
How can I tell if my alternator is good?
If it’s below that, charge the battery with a battery charger before you conduct the test again. Then start the engine and check for increased voltage readings. If you see higher readings, chances are the alternator is good. (More sophisticated testing equipment is needed to detect an open or shorted alternator diode.)
What should the resistance be for an alternator?
If all this checks out then I suspect you have a wiring issue. I would perform either a voltage drop or resistance measurement of each of the wires from the PCM to the alternator. Also, through the fusible link from the battery to the alternator. You should have less then a half ohm of resistance.
Why is the battery light still on after a new alternator?
So, now truck has new alternator and battery BUT battery light is still staying on. I had them check both and they said, new battery and alt showing good. I know all of the connections are tight and I checked the fuses inside the truck and all are good.