Alternator overcharging

[FiveSeventyZee]

So I've had issues with my battery losing a charge sometimes and I thought my alternator might be weak. I got on the internet and did some research and got around to checking it today. I found that it should be charging at or around 14 volts and when I checked mine it was pushing 40 volts, at about 37-38 volts.

 

I checked the battery to make sure my voltmeter wasn't busted and it was fine, the freshly charged battery showing 11-12 volts.

 

So any clue what might be wrong here? also, what problems might be caused by this?

 

Thanks

[dan5138]

Where are you checking output voltage at? And what year of Z are you working on?

[roger.svoboda]

alternator voltage regulator is bad or connections are incorrect. some alts internal regulator some external depends on the year.

[Kris.Is.Awesome]

If you were using a voltmeter make sure it was on DC, not AC.

 

It's a mistake anyone can make (I've done it before).

It's easy enough to just set the meter without really paying attention.

 

Shot in the dark though!

 

It will show up as a number like that

[FiveSeventyZee]

Where are you checking output voltage at? And what year of Z are you working on?

I checked at the positive wire on the alternator. Its a 72 s30 however its a SBC swap with the alternator from the same 89 camaro the engine came from.

 

alternator voltage regulator is bad or connections are incorrect. some alts internal regulator some external depends on the year.

Where should the connections go? I've never really done much with an alternator before other than replacing one in my 80 720 which was just an unplug and plug in the new one.

 

If you were using a voltmeter make sure it was on DC, not AC.

 

It's a mistake anyone can make (I've done it before).

It's easy enough to just set the meter without really paying attention.

 

Shot in the dark though!

 

It will show up as a number like that

I was measuring it in DC volts. This is one of those things I was checking when I was in disbelief at the 39 volt reading. But it was in DC volts (the 50 volt range) and the battery measured fine on the same setting and same voltmeter.

[letitsnow]

Did you remove the factory voltage regulator? Have you had a parts store test the alternator?

[FiveSeventyZee]

I haven't done anything to the alternator since I've had the car. I did this test so I could see if something was wrong before taking it off, but I guess I could take it off and take it to get tested.

 

I'm thinking a new single wire alternator might be an easy way to fix this problem.

[WreZ]

i think roger and snow hit it on the head, it sounds a lot like a voltage regulator problem

[letitsnow]

I bet the voltage sense wire is messed up somehow, it escapes me as to which one it is right now, but it should have the same voltage as the battery. This tells the voltage regulator inside the alternator what to do.

[Hitman Z]

I am with the guys too, it looks like a bad voltage regulator.

[FiveSeventyZee]

I went to check the wiring to see if the ground was okay, if it can't ground it can't dump the extra volts. I discovered it's a Hitachi alternator, checked my Haynes manual and sure enough it's stock from the 240. I also discovered that the voltage regulator is external, and still there, no clue if its good or not.

 

I'm thinking I should get what I thought it was, a chevy alternator.

 

Now I need to know if I should get a one wire alternator or a normal chevy alternator. Either way I'm getting one with an internal regulator. Also most alternators on jegs and summit are high output alternators, could I run into any problems running a high amp alternator on a relatively normal setup? (mechanical fuel pump, for now, no major stereo plans, really no huge electronics plans) Or would I be fine with some 100 amp unit?

[FiveSeventyZee]

Okay so I have a new alternator but the JTR manual says to install a 14 gauge fusible link for extra protection. What amperage is the fuse supposed to be? I found one that's 30A, is that one good?