In this situation it's probably a bad alternator. The brushes could be worn out. Are you sure it's your alternator? To check, start your vehicle and put a volt meter across the terminals on your batter ( pos to pos, neg to neg ). You should read from 12 to 14 volts. If it is lower your alternator may be bad. Also check that you have no shorts in your main battery cable. To do this, disconnect your battery (negative cable first ) and put the positive lead of your ohm meter to the disconnected positive cable and the negative lead to ground ( your disconnected neg cable will do ). You should read infinite resistance; if not a short may be causing your battery to lose a charge. If neither of these things is the problem your battery may be going bad and not holding a charge. To test this pull it and put it on a trickle charger. Most battery chargers will warn tell you if the battery is bad. If you leave it on a slow charge and don't see a higher voltage in 2 hours your battery is probably bad. Most part stores will test your alternator and battery for free but you will have to take them out and to the store.
If the battery light is on, it usually means that the alternator has a problem. Have the alternator checked at a local auto parts retailer. If one or more of the diodes are bad, your battery charge will be affected.
The problem is not the starter. The battery is either not holding or not receiving enough charge. Problem could be (1) loose alternator beltl (2) loose/corroded battery cable(s); (3) dead cell(s) in the battery; (4) bad alternator.
The answer is no . The battery starts you vehicle , the alternator charges the battery so if your alternator is bad your battery is not receiving a charge which will cause a "no start" condition.
YOUR ALTERNATOR IS BAD THE REGULATOR INSIDE THE ALTERNATOR HAS SHORTED OUT BUT MOST OF THE TIME IT WILL STILL CHARGE
I had this problem in my 1990 Ford F150. The battery cables were bad and weren't carrying the charge from the alternator to the battery
When the alternator starts charging the battery voltage will increase about two volts to charge the battery.
You either have corroded battery terminals (where cables hook on battery)or a bad alternator ...Autozone willtest for free
If your car doesnt start, it could be the battery. But if the car starts and you unplug the negative cable and the car turns off, its the alternator.
If the engine will not even crank, then suspect a defective battery or starter. Start by removing both battery cables and cleaning the cable connections and battery posts. Reconnect them and see if it starts. If not put a battery charger on the battery and fully charge it. If it will not accept a charge is is defective. It the vehicle starts then you may have a defective alternator. If the battery is good and it still will not start, suspect a bad starter. You will have to remove it and have it tested.
The battery "starts" the car...after that the alternator keeps the battery charged. They work together in other words.
battery not holding charge or may need a new alternator
Yes, the battery starts the engine, and as long as the battery is fully charged the engine will start. The battery will loose it's charge if the alternator is defective and not replenishing the charge of the battery but the alternator has nothing to do with starting the engine.