Hey Scotty, I have a 2005 ford focus with 184,000 miles and about a week ago I had the battery light come on when I put it in park. I went to AutoZone to get it tested and they said it was my alternator, which makes sense considering my battery is just a year old and I don't run any big speakers, just an aftermarket radio and normal aftermarket speakers. My mechanic tested my battery and alternator and says the battery is weak but the alternator is fine. The alternator was charging at 14.1 to 14.6 amps according to him. But the battery was only charging at 9 volts. I go back to a different autozone and they say the battery is at 100% capacity. Please help me know what to do next! Thanks!
I'd go with my trusted mechanic over the local parts store personally.
The alternator was charging at 14.1 to 14.6 amps according to him.
I think you are confused. 14.1 to 14.6 sounds like voltage, not current (Amps).
It's a healthy voltage for an alternator.
But the battery was only charging at 9 volts.
The charging voltage is always the same on both alternator and battery because they are directly connected to each other. Maybe you meant 9 Amps?
Charge current depends on the battery state of charge. If the battery is fully charged, then current will be low.
a week ago I had the battery light come on when I put it in park.
Has it come back since then?
If not, then maybe you just left something on and the battery really was low.
If you don't have don't have a battery light, and don't have problems starting, then just enjoy your car 🙂
You could perform your own test by starting the car and turning on lots of electrical devices like the lights, radio, blower fan, etc. If everything is still good after 15 or 20 minuets than the alternator is working fine. If the alternator were failing you would experience dimming lights, slower fan speed and so on. The engine will start to idle rough and might even stall.
Another indication the alternator is OK is the voltage readings. 14.1-14.6 volts is normal. 9 volts is quite low. (I think you confused amps with volts) Typical alternator current output is more like 60-100 amps. Go with the mechanics diagnosis like @mod_man said. The one year old battery should still be under warranty. Let me guess, did it come from autozone?
Sounds like some strange readings for sure. If you get a simple volt meter, if the car is off, it should ready between about 12.2 to 12.8 volts normally. If you just turned it off, it may ready higher. If the car is running and you test the battery, it should read between 13.5 and 14.5 volts, give or take, indicating the alternator is charging.
If you do @rth3rth3 test of running the car for a bit, if it doesn't stall after a while, and the lights don't dim, the alternator is likely working.
If the battery were at 9 volts, that would indicate that it is basically dead, likely a bad cell. As @mmj said, if it starts and runs okay, both are probably good.
I suggest checking your battery terminals for corrosion and tightness, also check to make sure the power cable is fully in the alternator. I recently had a friend that the thing was loose, at first I thought it was a dead alternator because the volts were too low while running.
