New alternator (on 2nd) and battery--but losing power (car dies).

Hello.

With a new battery & new alternator:
Two weeks ago, I was a red light during rainy weather and my P5's radio and dash lights basically went bonkers flickering and such. I managed to park a block away and turned it off but it would not restart; when I turned the key, I was getting a bunch of quick clicks, but no cranking. I still had lights, however. Again, this is on a new battery and alternator.

AAA came out and told me that the (new) battery is not holding a charge but the alternator "seems fine" (based on voltage). They easily jump-started it and I drove it to the mechanic's. They resolved that it was the alternator, and replaced it again. I don't know what basis they used to determine this, but I believe it was an incorrect assessment. Note that they didn't replace the battery, as it was new and the cells were fine.

Something about the car seemed off to me, still...especially when it was raining a lot.

Fast forward six days:
It was another rainy day (but hardly), I'm driving off from a Starbuck's drive-through and the lights flickered and yet again, I lost power. This time, the car was making buzzing/humming sounds when I turned on the hazard lights--without the key being turned or inserted at all. If I shut off the hazard lights, the buzzing stopped. Unlike two weeks prior, I was only able to hear the rapid clicking a couple of times, then it completely stopped. Eventually, the hazard lights stopped working, too. It couldn't draw enough power to do the most basic thing: e.g., run the hazard lights.

AAA came out and easily jump-started it, but fearing it would die out while I drove off, I towed it to the mechanic's anyway.

So, now the problem is presenting itself despite having a new battery and being on its second "new" alternator.

Does this match your issue? What was wrong with it? What was done to resolve it? What did it cost?

From a bit of research I've done online, here's what could be wrong:
-- ECM water intrusion. (It is happening during very wet, ongoing rainy weather. What would be the symptoms, exactly? Would this match what I wrote above? Would there be a trouble code?).
-- Wrong alternator (but twice in a row is highly unlikely).
-- Blown master fuse or fusible link. (What would be the "symptoms"?)
-- Parasitic draw/draining (I doubt this one).

Lastly, I should mention that I don't any trouble codes.

Thank you for your time! I appreciate the help.

NM

Double check the voltage on the battery first to make sure it is legitimately working. It does sound like something to do with your charging system since the car can be jumpstarted to get it working. I doubt it would be a Master fuse since the car wouldn't start without it but wouldn't hurt to check your fuses anyways. I also don't think it would be a parasitic draw since once the car turns over its running off the alternator not the battery. It could be that the connections for the alternator that physically plug into the alternator could of been plugged into the opposite locations. Also could be wrong alternator like you said but is very unlikely, then again it is humans working on the car so you never know. As far as the ECM water intrusion, Im not sure exactly what would happen with that as I live in the desert so i dont have to worry about that. Regardless i think it would short the system out and could stop the car. Thats a tough situation to try and diagnose hope I helped a little bit and good luck on figuring it out!.

This is going to sound stupid and possibly insulting to whomever is/has worked on the car, but check all connections to make sure they are tight. If battery cable or alternator connector aren't tight, well, you could have the issues you are having. Also, don't rule out the alternator, no matter how "new" it use. They are usually refurbished. I went through 4 in about 4 months till I finally got one that has lasted me a few years now (fingers crossed!)

Thank you so much for the reply! Much appreciated.

Thank you. I'll post the results here as soon as I know what's up!

There is an easy old-school test for the alternator,.. Just disconnect the negative battery terminal while the car is running.

If your car keeps running your alternator is fine if the car dies the alternator is bad.

Some guys on this forum said NEVER do this,.. you'll blow s*** up due to power surges (like the ECU for example)

I've done it three times on my car with no problem,... I'm sure the car is designed to deal with it.


One less risky thing to do is to check the voltage on the battery before you start it, then measure it again while the car is running. The voltage should jump to 13 volts or more.

The alternator on our car is controlled by the ECU with a separate wire from the ECU to the alternator. This wire can be a problem. If there is a bad connection between the ECU and alternator, the alternator effectively "shut's off".

Been a while since I've heard of that old trick! ^^ Almost completely forgot about it, thanks for the reminder

also check the belt and tension of the belt that runs the alternator, make sure is not slipping due to rain or being wet

...and be sure to check and clean the grounds from battery terminal to body, and to engine.

I meant to come through here and update everyone on the results of my (two) new alternators failing. As it turns out, the alternators they were trying were not powerful enough to handle the car's needs. They wound up installing the most powerful/expensive one they could find and that did the trick. I was trying to save money and they put in a lower quality alternator. Don't go that route--even if they say it's "OE" or rated for your vehicles. I have not had any issues since they put in the better alternator.