Trying to understand my charging system
2013 Thor Daybreak F53 Ford Chassis: My battery light comes on about 30 seconds after I start the engine and stays on. The battery checks good and I am getting 12.7 volts not running and 13.5 volts ru...
Forum Discussion
A person has to be VERY careful doing this, but if the alternator is faulty due to a shorted or open rectifier or shorted or open stator winding they get hotter than Hades. Hot enough to give a 2nd degree burn. Hot enough to turn stator winding varnish black.
By the same token, starting the engine and letting it run to charge low batteries will heat the alternator up as well. The difference is, voltage will be low and not rising with a bad alternator and with a good alternator voltage will be rising briskly.
Might as well paint by the numbers here...
Grab a 12 volt test light.
You need to test every last chassis fuse in your vehicle, whether under the dash or under the hood. Do every last one, with the engine running and headlghts on.
If you find a dead fuse, replace it. Checking won't cost a nickel.
Another less known professional trick is to use an AC meaning alternating current voltmeter. Measure voltage right at the alternator. Yes the meter isn't supposed to read a lot of AC voltage. If 2.0 volts or greater is seen, then the alternator is bad. The old Sun VAT 33 and VAT 40 wheeled charging system testers use 3.0 volts as the magic threshold between good and bad. Any alternator with 2.0 volts is bad. No if, and's or butt's. Many digital meters go nuts trying to read ripple either AC or DC. I use an analog meter.
Most Parts Store rebuilds are garbage. Find a store selling your make of vehicle authorized rebuilt alternators. It is common for parts store garbage to lose 15 amps of maximum charging ability at idle under load as compared to original.
When I was rebuilding the CS series Delco alternators or the 2G 3G or 4G Ford alternators, a burned stator would be replaced with a brand new factory stator. Same for rotors. I could "get away with" using rewound parts in older alternators but not in the newer ones. Test bench performance does not lie.
By the same token, starting the engine and letting it run to charge low batteries will heat the alternator up as well. The difference is, voltage will be low and not rising with a bad alternator and with a good alternator voltage will be rising briskly.
Might as well paint by the numbers here...
Grab a 12 volt test light.
You need to test every last chassis fuse in your vehicle, whether under the dash or under the hood. Do every last one, with the engine running and headlghts on.
If you find a dead fuse, replace it. Checking won't cost a nickel.
Another less known professional trick is to use an AC meaning alternating current voltmeter. Measure voltage right at the alternator. Yes the meter isn't supposed to read a lot of AC voltage. If 2.0 volts or greater is seen, then the alternator is bad. The old Sun VAT 33 and VAT 40 wheeled charging system testers use 3.0 volts as the magic threshold between good and bad. Any alternator with 2.0 volts is bad. No if, and's or butt's. Many digital meters go nuts trying to read ripple either AC or DC. I use an analog meter.
Most Parts Store rebuilds are garbage. Find a store selling your make of vehicle authorized rebuilt alternators. It is common for parts store garbage to lose 15 amps of maximum charging ability at idle under load as compared to original.
When I was rebuilding the CS series Delco alternators or the 2G 3G or 4G Ford alternators, a burned stator would be replaced with a brand new factory stator. Same for rotors. I could "get away with" using rewound parts in older alternators but not in the newer ones. Test bench performance does not lie.
