The only thing the starter and the battery have to do with each other is that they both have 12v going to them..... nothing else. So was no need in changing the alternator just because the starter was bad. Like saying "I changed my tires out, so for prevenatprev measures, I changed my headlights bulbs as well", lol.
Alternator charges the battery, that's it.
Did you replace the starter and alt with factory parts or off brand units? Connections super tight at both? If you can twist any connection with your hand, no matter how much force you use, it's too loose.
With all that said, your problem seems to be your battery, like others have said.

V.

 

 

 

 

 

Glad to hear the problem is solved. A sulfated cell will vex you. AMHIK.

 

 

When testing a battery, you need to check the amperage, not only the voltage.
You can have a faulty battery that reads 12v, but won't have enough amps to crank the engine over.
You need to test the battery when the load is applied, so when the engine is attempting to start. A faulty battery could read 12v at rest, but when you apply the load to it, from the starter when attempting to start, the voltage will dip extremely low, and prevent the vehicle from starting.
This is also why a faulty battery will also read 12v, and have enough amperage to run the radio and other light load accessories, but will not have enough to start the engine.

 

Exactly. I've had batteries with sulfated plates and this is exactly how they behave. I have also had batteries with internal faults completely dead and never able to recover. Age is usually a factor, but manufacturing defects also cause poor battery performance earlier in their service lives.

 

 

In the OLD days, before Voltmeters, cars had Ammeters. Actually I found Ammeters a better indicator of the battery condition then the Voltmeter. I looked for an Ammeter on my OBD wireless reader. No where to be found

Lou

 

Battery load testers are pretty cheap these days. Just puts a load on the battery. Like mentioned above, good voltage can mean absolutely nothing.

V.

 

If all you have is a voltmeter, you can hold it on the battery and monitor it while you have a friend attempt to crank the engine. You will notice the voltage dip down low on a faulty battery when you attempt to crank. If the voltage dips too low, the electronic components will shut off, and you will get nothing out of them. If the battery is faulty, it may take a minute for the battery to recover up to a voltage that is acceptable for the electronic components to come alive again.

In the old days, you would get dim lights, and a slow cranking alternator. Now, when the voltage is too low, you just get absolutely nothing. Electronic control modules will not function at all if the voltage is too low.

Also, for future reference, if you are having electrical issues, the source voltage (in this case the battery) is always #1 thing to check thoroughly. Without good source voltage, ECMs and modules do some really weird things, and I have seen techs chase these weird issues, without confirming they have a good source voltage in the first place.