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Go through the basics.
1 Make sure the alternator is charging (operating properly) by measuring the voltage between earth (battery negative) and the live terminal. It should be greater than 13 volts, less than 15V.
2 Make sure the regulator is being excited. Most modern alternators need to have the dash light working in order to send a minute current to the alternator regulator to kick it into life. If the dash light is out, (fused) the alternator won't work.
3 If the voltage from the alternator live terminal is good, check the voltage at the battery. It should be between 13.5 and 14.8 Volts. If this reading differs from the reading at the alternator output, you have a wiring issue.
4 Wiring issues may include but is not limited to:
a) bad connection at the battery terminal
b) bad connection at the main fuse,
c) bad connection at the starter motor. Some vehicles pick up the main power from the battery cable at the starter solenoid.
d) broken wire, bad connections on the main power lead connection terminals.
1 Check battery terminal connections, clean and tighten if needed
2 Check voltage at positive terminal of battery while engine is running with multimeter, should be between 13 and 14 volts
3 If voltage is lower, alternator may be bad (not charging battery)
4 If voltage is good, battery may be bad (not holding charge from alternator)
Check wiring integrity and clean connections. While running, check alternator output voltage from terminal on back of alternator to any suitable ground on engine or neg. battery terminal. Should not read over 14.2 volts. If over that or fluctuating more than.5 volts, bad alternator, return as defective.
you can try cleaning the battery terminals to see if the battery has a good connection I had this same problem..take it to someone who can test the alternator to see if it is charging the battery when the motor is running...if it is not.charging it will kill a battery very fast...most auto part stores can test it for you..they are expensive to replace cost over 200 bucks. take it to a shop that can rebuild it..had mine rebuilt for 60 bucks and it just as good as new..if the alternator isnt the problem...check to see if anything is stuck in the on postion..trunk light..dome light..etc. if this problem started very quickly it is either the battery connection needs cleaning or it is the alternator..
first thing i would check is the alternator it should read 13.4 to 14.6 volts while running. if the alternator isnt charging than the vehicles computer is not getting the required voltage to run all accesories and engine parameters. i hope this helps
Jump start this truck if possible and do this with a volt meter. While the engine is running connect the red terminal of the volt meter to the negative terminal of the battery. Take the black probe to the volt meter and connect it to the positive terminal of the battery. The reason why is to test the diode if its any good. If you get a reading of voltage the diode is bad and will not let the altenator charge your battery. The diode is made for DC current to run one direction. If runing both ways no charge will be directed to the battery
use a volt meter while the car is running to check the main wire or large red wire coming off the back of the alternator it should read a steady 14 volts, the volt meter must be set at dc 10 amp settings, ground the black wire to ground or a metal surface some where on the car and touch the red probe wire on the volt meter to the main terminal of the alternator as i said it should read a constant 14 volts if it doesn't the alternator is bad.
CHECK THE BATTERY TERMINALS, THEY MAY NEED TO BE REPLACED. BEFORE YOU REPLACE THEM, CHECK THE PLUG ON THE BACK OF THE ALTERNATOR FOR TIGHTNESS AND CORROSION. ALSO CHECK THE GROUND WIRE ON BOTH ENDS. I HOPE THIS SOLVES THE PROBLEM. THANKS FOR USING FIX-YA. PLEASE KEEP ME POSTED. GOOD LUCK
I found the problem YEAH. It was the fuse that is in the side of the fuse box under the hood, Its where the battery wire from the alternator connects thru a fuse to go to the battery, Its one hundred and something volt fuse. It took care of the problem instantly.... Thank you all for your replies...