Alternator issues

[gullwinger]

Hey Guys,
I just took out the Motorola alternator *batter light did not come on when key is on, however is did when I reved up motor and volt gauge showed 13 volts after rev up. So I replaced with Herveys alternator. After replacing wires my new alternator does not charge (volt meter no change, light does not light up). I replaced the bulb with a #161 but still not working. Im thinking there is a problem with the Brown/yellow wire???? any one got any ideas.
Thanks
Jason

[Morpheus]

The battery light should illuminate when the key is turned on, and should go out once the car starts. If it comes on when the car is running and driving, it means the alternator is not charging, and you should pull over to inspect the situation immediately. In my case, this happened once while I was driving. It turned out that my alt belt broke, which can cause a BIG problem considering it's also your water pump belt.

Make sure that the single wire is indeed connected to the brown wire with the yellow stripe. On my current car, the PO had connected the alternator to the solid brown wire by mistake.

[David T]

It is also possible the alternator is just bad (or the internal voltage regulator). Most places test for free so if you take it off they can check to make sure if it is the alternator. If it does test good then you must suspect the wiring (or the bulb) in the car.

[Ron]

Hey Guys,
I just took out the Motorola alternator *batter light did not come on when key is on, however is did when I reved up motor and volt gauge showed 13 volts after rev up. So I replaced with Herveys alternator. After replacing wires my new alternator does not charge (volt meter no change, light does not light up). I replaced the bulb with a #161 but still not working. Im thinking there is a problem with the Brown/yellow wire???? any one got any ideas.
Thanks
JasonI'm confused as to why change the bulb if it came on when you revved it??

Try this (if anything is not correct, stop and report back):
1. Make sure that disconnecting and grounding the Brown/Yellow wire makes the light come on when the key is in the "Run" position.

2. Make sure the main wire(s) (large Brown) has 12V+ on it and is connected to the Main Alternator terminal, and, the small Brown/Yellow wire is connected to the field (single wire on Alternator).

3. If the light does not come on when the key is in the "Run" position (engine off) now, the alternator is bad (probably internal regulator/field circuit).
If the light comes on when it is running, the alternator is bad (probably an internal short- diodes/windings).

[gullwinger]

This is my second alternator from specialtauto. The same problem with the light not turning when the key is on.
So I changed the bulb and no change. The belts new and tight I'm just thinking it may be the brown yellow wire