Alt and Battery Question

How can you tell if your alt and batt is going?

06 tacoma base. 1 diehard platinum up front a group 34 prob. a 2 battery out back next to the amp a optima group 31 battery 3-4 year old 4-5 year old rf sub amp 100 bdcp sundown 100.4 amp. my voltage read low 12.8 when im driving 12.4 when idle gonna have a friend bench test the alt and the battery soon any help thanks

 

If you are running a high power audio system, you should consider a high output alternator, say 200 or 250 amp. These guys have affordable high output alternators:
http://stores.ebay.com/BNR-PARTS-ALTERNATORS-AND-STARTERS/Toyota-/_i.html?_fsub=9379725017

The battery voltage should display 12.5 volts or higher before starting engine. Voltage reading alone may not show ability to turn over engine. You need to do a load test on the battery, using a load tester or take car to AZ or alt shop to test battery and alternator system; most will do it free of charge.

As for testing alternator...with engine warmed up and idling, voltage should read 13 volts or higher. Then do a load test...turn on fan on high; turn on headlight high beam; and wipers on high (do not turn on AC as that applies mechanical drag which will throw off readings); voltage drop at idle should be less than .6 volts. This is assuming all connections are properly connected and corrosion free. There is a voltage drop test that you can look up for yourself.

http://www.aa1car.com/library/2003/us20310.htm

http://www.aa1car.com/library/charging_checks.htm

 

If I was a betting man, I would say that your alternator is not putting out properly, or the voltage regulator is not working. Even then the regulator is in the alternator so yeah Alternator.

 

Ahh