Trying to understand my charging system

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.

Yes, do what MEX is saying. There are some instructional videos on youtube that explain how the newer modern charging systems work. Not the same as old school any more. Sorry but I don't have the search criteria but if you search something like "modern charging systems tutorial" you'll find it on youtube.

If it continues to be a problem and your battery fails to recharge, it may be time to see a Ford dealer for further diagnostic advice.

Chum lee

• Start the engine. Let it warm up for 10 minutes
• What voltage do you read?
• Start vehicle air conditioner on high. Voltage now?
• Turn on headlights high beam. Voltage now?
• No not shunt anything off until the end of the test
• This is a progressive loading test.

Things are not as easy as they used to be. With today's systems the ECU reads system voltage at three points and analyzes the FIELD REPORT of the alternator. If voltage climbs TOO SLOWLY, the check engine light will come on.The ECU compares rotor excitation amperage to how fast the voltage is climbing. A cute test is to connect a battery charger and maintain correct voltage with a heavy load. A ECU can discriminate sample voltages and throw an error code.

Normally when a new alternator malfunctions the light comes on and stays on after the key is released.

The delay makes me suspicious. I would want more proof before condemning the alternator.

Of course there other further tests to be made but this one will do for a start.

The solenoid is behind a circuit board so I cannot remove the wires from the small terminals, however I was able to get a probe on the nuts to check voltage.
I have full battery voltage to on and nothing on the other. I think that is the way it should be. I did pull the aux/start switch and it seems to function OK.
I think I am going to take it to the shop and have it checked out before I start changing parts at random.

Thanks for the help
Jeff

Output should be around 13.5-13.9V from the alternator with engine running.

My last one started to put out 14.5 to over 16V.
That make my ABS light come on as too many V going to it. I replaced it right away. New one puts out 13.6 to 13.9V by my VMSpc program.

Have you tried disconnecting the small lead that goes to the solenoid from the Auxillary switch to see if the switch is faulty? That lead being constantly closed could be placing a load on the circuit lowering the voltage slightly.

That's kind of what I was thinking, it should be putting out closer to 14.5 volts. Just can't figure out why that solenoid is closed.

Have your alternator checked. I suspect it is bad, or your missing a belt