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Re: Charging issues - ongoing Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 2 Dec 2003 09:18:50
In Reply to: Charging issues - ongoing, Shawn C., Tue, 2 Dec 2003 08:31:32 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The excitation wire goes from the ignition to the BATT light on the dash. From there it goes to the alternator.
The alternator uses electromagnets to create a magnetic field. When you turn the key to ON, current flows from the battery, through the BATT light, and into the electromagnets in the alternator. This current creates the magnetic field that allows the alternator to start up. Since there is current flowing through this wire, the BATT light bulb lights up.
Once the alternator starts producing power on its own, it takes over driving the electromagnets (field coils). Since the alternator is supplying the current now, no current flows throught the excitation wire. No current, so the bulb goes out.
First, it's critical that the bulb come on when you turn the key to ON. That shows the current path is complete. The light should go OFF when the alternator kicks in. If the alternator is working, you should NOT see the BATT light when the car is running.
It's also important that the BATT light bulb is the exact right light bulb size. No substitutions. It's different than the other dash bulbs. That bulb sizing sets the excitation current to ensure the alternator starts up right.
There is an outside chance that even with the right bulb, and good wiring from the bulb to the alternator, that the alternator won't start up all the time. Alternators get old, and their efficiency can drop off. It's possible that the alternator isn't getting quite enough excitation current to start up reliably. It worked on the bench because either it got a little more current than in the car, or they tested it once, and it happened to work that one time. It's just a build-up of tolerances, and working on the bench isn't a guarantee that it'll work in the car. In that case, I would recommend replacing the alternator. A decent rebuilt unit runs about $125-$140, and you've got to be tired of paying the labor charge of getting that baby in and out.
posted by 192.249....
, Tue, 2 Dec 2003 10:48:04, Tue, 2 Dec 2003 09:18:50 <-- Viewing This Message, Tue, 2 Dec 2003 11:02:26, Tue, 2 Dec 2003 13:03:36
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