Alternator question

[Striker36]

Testing my alternator on a 1991 5.7 Alpha, and I have a question. Both my batteries with engine off are reading around 12.5 volts. With engine on, no matter what speed, at the batteries Im seeing 13.8 volts. All the test procedures Ive read seem to suggest it should be up in the range of 14.4 volts. Pretty sure my meter is accurate, does this indicate a problem of some sort, or is 13.8 normal?

 

[Bt Doctur]

13.6 -14.6 is within normal

 

[Striker36]

Great, thanks. I was hoping not to have to pull anything else apart.

 

[stonyloam]

Assuming you are using a digital meter. A new fully charged 12v battery will read 12.6 volts, so you are fine there. When running you should be putting out "about" 14v you are at a constant 13.8v and your battery is staying changed, so you should be fine. Remember when you are running you are using some current to run the engine which will drop the voltage a bit. A problem would be indicated by a significant deviation, either the voltage staying below 13v or above 15v when running. Watch your voltage when you start up. If the voltage drops immediately after startup then comes up to about 14v and holds steady everything is working as it should.