goofy ammeter - bad alternator?

[Asha'man]

Got a new battery the other weekend (as per my other thread) and now my ammeter is all over the place. With stereo (almost totally stock, so no huge power drain) and headlights on, it'll go down to the first notch within a few minutes. Second notch is normal, and I just started it up and it was well past halfway to the top. Alternator going bad? I guess I'll go 3G if I replace it, but I'd really rather not have to. Suggestions?

Ash

 

[351wcoupe]

put a meter on the battery and make sure its at least 12V 12.66 is considered 100%.
Then start it and see where your voltage is. maybe 13-14V. Then turn on everything you can AC, headlights, radio, wipers Etc. Should go down and then come back up to wherever it was 13-14V.
Crude but requires no special tools.

I had a guy come into autozone after doing this test I told him. He said I don't know......I guess its not charging the testlight dimmed alittle.

 

[Red_LX]

Hmmm...well, my car did something similar to that when the old alternator died a couple years ago. You could start the car, but the voltmeter or ammeter or whatever it is was only on the 2nd notch from the bottom, usually it runs a little over the middle.

 

[mr_woodster]

Like 351 said, put a volt meter on it. Mine gauge died a week or so ago...i about freaked out, put the meter on it when i got home...all was fine. In short, never trust a mustang gauge!

 

[Ray III]

Three demerits for you for calling a voltmeter an ammeter.