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Brake application radio fade

The vehicles speedometer began to pulse with the beat of the blinker and the volt light started to shine like a beacon. The car died. I replaced the battery,cleaned the battery cables,starter terminal,and starter cables. The car started. Then two days later after very minimal driving more issues. The volt light is on again and the radio is fading out with the application of the brake. The passenger side brake light has been a constant issue and it is not the bulb. Now the car will no longer start on a battery that is three days old and has less than two hours of use on it. Any insight?

The alternator is the heart of the battery. It keeps the battery alive. Have the alternator tested at a large auto parts store or find a good mechanic and find out if you need a new alternator installed. I think you do.

Alternator is getting 12v. So I believe that to be good. I am not an auto electrician however.

What the alternator "gets’ is important but even more important is what it “gives” what is your alternators output in both volts and amps, under load

Saying the “Alternator is getting 12v” doesn’t say anything. In fact it indicates a problem.

If the alternator is only producing 12 volts, then that could be problematic. The voltage should be up in the 13.5v range. And it must be able to sustain that voltage while producing its rated amperage output (ie under load).

I think something else is going on to cause your problem, but don’t be fooled to believing your alternator is OK just from seeing 12v.

I was looking at "gets’ as in field excitement.

I’ll bet the alternator is shot, and you’re running purely off the battery and it’s stored charge. Without the alternator restoring the charge in the battery, it is going flat. A simple test is to start the engine, then read the voltage at the battery. If it is 12v or less, the alternator is not working. It should be 13.5v to 14.5v for a properly working alternator.

Anytime I observe problems like you describe I suspect ground problems. So check and/or clean the battery negative to engine ground; battery negative to body ground(s); any body to engine ground straps; and body to instrument panel grounds. There are other grounds to the ECM(s) so check those also.

Let us know what you finally find with this situation.