Battery light on, Battery not charging code on dash, voltmeter on dash shows 12 volts only, Occasional service break booster falt on dash readout. Truck has a new battery. Is it alternator? Or other problem? [email protected]

Hi if the alternater has packed up then the ecu has put these falts up becouse it sees a falt in the system ,get the alternater fixed and then the other falts should wright there selves,hope this was some help.

Alternator , brushes or the regulator are going bad !

Test the alternator. The battery light is for the charging system. Once the charging system is working with the engine running, the light should go off. If your light stays on with engine running, the alternator may need service or replacement.

To test the charging system, just put a voltmeter on the battery with engine running. The voltmeter should register at least 13.5 volts- alternator is charging. If you only show battery voltage with engine running, like 12.2-12.8 volts, the alternator or charging system is not working. The battery light should be on to signify this.

Clearly, the battery is either dead or the power from it is not reaching the starter circuit. The battery is used only to start the engine and the alternator provides power for the car once started. Since the car shuts off when the booster cables are removed - I'd make sure all the connections at the alternator are made up tight. I'd also have a check on the fuses for the alternator's output. A voltmeter on the battery should provide 12 - 12.5 Volts when the car is off and 13.5 to 15 Volts with the car running. I suspect you only see those voltages when booster cables are connected.

Sounds like you have either a dead battery or a bad connection on the positive/negative terminals or the starter motor or the ground to body connection? It is also possible for the cable to have corrosion built up inside the insulation causing a resistance? Clean your battery terminals first then if a charger is unavailable using booster cables connect the positive cable to the dead battery then the positive cable to the jumper battery then connect the negative cable to dead battery and positive cable to jumper battery and attempt to start the car if same conditions then the xonnections may either be loose or corrosion hampering voltage to be supplied efficiently! A digital voltmeter will or should show a 12-volt reading on the battery if less than 12-volts the battery needs to be charged or replaced?

Brother Mark, changing the battery with a new one being done won't make the light go out, as you noticed. Light is still on so you changed the alternator. Good, but the battery light is STILL on. This only means that the charging circuit from the alternator is not working in the voltage regulator or the wiring is not connected properly to the alternator/regulator. A new battery will show over 13 to 13.5 volts not connected. An old battery will still show 12 volts and still be weak or bad. After connected and engine running, the system will show at least 14 volts because alternator/regulator is working properly, using a voltmeter/load tester connected to the battery. If after replacing the battery and alternator it is still reading 12 to 13.5 volts, it is not working and the light will stay lit on the dash. You may have purchased a faulty alternator if the system tests out this way. Have your system checked with a volt meter or load tester bit be sure all the connections are proper and clean.

Maybe it wasn't running long enough to charge up the battery?
Stop trying to jump it, when you are having problems with it dying, take the battery off and have it charged. And/or buy a $20 voltmeter to see what the battery shows. If it says less than 12 volts, it is discharged, and needs charging. A good battery that is not run down should have at least 12.5 volts. A new battery that is charged should have very close to 13 volts, maybe 12.8 volts.
When you have the truck running, check the alternator for charging. You put the voltmeter right on the battery and check it again. This time, with truck running, battery should show at least 13.5 volts. That shows the alternator is working. A good alternator will put out about 13 or 14 volts-the regulator will keep it from going any higher to prevent problems, like a melting battery or electrical parts burning out.
I would say get the charging system working right, then address the problem of dying at stop lights. That could be a carburetor problem, if the alternator is working.

If the lights drain the battery when the engine is running, then you have a bigger problem of the alternator not charging, not working. When the engine is running, the alternator supplies all the current to run the car's electrical systems, while also charging up the battery for the next start-up. If you know the alternator is good, then maybe a fuse or fusible link has blown, preventing the alternator from working. To check, put a voltmeter on the battery with engine running-it should show over 13.5 volts if the charging system is working. If the alternator is not putting out, the voltmeter will read same voltage on the battery as when the engine is not running. A fully charged battery should show "around" 12.6 volts. A discharged battery will show less than 12 volts. That should give you an idea of the range to look for on a voltmeter. I believe some parts stores will check the voltage for free. I know most stores will test the alternator and battery for free if brought into the store, but you need the voltage read while on the car and engine running. If the system is charging normally and the lights kill everything, you may have a short in the lighting system.

start the car. if you have a volt meter at the battery you should have 13 to 14 volts while running. if not your alternator isnt working.

Sounds like alternator if the battery is not staying charged or the output from alternator the big red wire is lost connection to battery +.
a voltmeter you can check with across battery and it should show minimum 13.8 volts minimum to be charging.
if the battery is low it should show 14.7 volts if it shows 12 volts or less with lights heater etc running then alternator is not charging.
You can get a cheap volt ohm meter from radio shack or walmart and use the DC setting 20 volt scale on meter and start the car and turn on everything and put the test leads of meter across battery terminals and see what the voltmeter says.