Testing the alternator?

[bushy]

Hey guys, is there a way to test the alternator?

It's overcharging my battery causing water to come out, but I just want to be completely sure before I start swaping parts.

 

[stock1g4g63]

If you have an Autozone or Pep Boys near you, most of those places test it for free.

 

[redtincan]

Pepboys is all a quick choice to get it check out, I would recommend you take the alternator out of the car. Driving the car if it’s overcharging can cause more damage (burn out headlight).

 

[DiamondStarM]

The simple at home test with a voltmeter is to test the voltage with the car off ( should be around 12ish ) and retest with the car running ( should be around 14ish ) and then turn on all accessories and you shouldn't drop more then a half a volt.

 

[turbodsm18]

When my alternator went bad it threw on my check engine light.

 

[bushy]

I'm not sure if it threw a cel.

I was just looking at the engine bay with the car on and noticed water coming out of the top of the battery, so I immediately turned it off.

 

[Old Mitsu Tech]

If the voltages are below 13 or above 15 I would suspicion the alternator as it's internally regulated. 13.5 to 14.5 is where I like to see them. If the battery is dead, it will show low until the battery voltage comes up to where it should be.

If it's not working, check the big post to make sure the wire isn't burned to the battery.

If it's ok, then have the alternator tested. You can remove it for this test.
Good Luck

 

[D_Eclipse9916]

If the voltages are below 13 or above 15 I would suspicion the alternator as it's internally regulated. 13.5 to 14.5 is where I like to see them. If the battery is dead, it will show low until the battery voltage comes up to where it should be.

If it's not working, check the big post to make sure the wire isn't burned to the battery.

If it's ok, then have the alternator tested. You can remove it for this test.
Good Luck

Mine goes frmo around 12 to 14 volts with no accessories on, and then with defroster, headlights, brake pedal down, and turn signals on it goes down to like 11, with stero on it goes to 9 WTF . All I have is a really small 4-channel amp too .

 

[DiamondStarM]

I would consider that a preliminary test and a reason to pull the alternator for a real diagnostic. Youll start killing batteries every few weeks like that.

 

[bushy]

Well heres a follow up:

We measured the voltage with the car off, and it was right around 13.

As soon I turned the car on, it shot up right to 17 and I turned it off.

Bad alternator I guess.