Help needed: 2013 Mazda6 won't hold charge or stay running

[rrubel]

(cross-posted from another forum, in case it looks familiar...)

Ok, I'm nominally a car guy, but this is our first Mazda. My daughter has a 2013 6 with the 4-cyl engine and automatic transmission that we've had since 2016, but this is the first real unsolvable problem I've encountered with it.

Symptoms: after a tire blowout, car wouldn't start (PROBABLY no connection between those). Got towed to NTB and was told battery was bad. Got new battery, TWO shops told us alternator was fine. The new battery does not stay charged, and the car will start when jumped but now sometimes dies while in motion and requires jumping to restart.

The real oddity is that when you rev the engine a little (in neutral or while driving), it ALMOST seems like the ECU resets because you get the two-tone startup chime and the HELLO message on the console. Also, blind-spot warning on mirror illuminates.

A voltmeter across the battery terminals while at idle shows 14v flowing to the battery, at least at THAT time. I personally suspect a bad voltage regulator that only intermittently fails, but I believe that is internal to the alternator so when several places tell me the alternator is working fine, I'm at a loss.

Anyone have any other ideas, or diagnostics to try? The engine is NOT throwing a code, the tire pressure light is on because it's cold and the tires are low, and the TC OFF light is on I think as a result of the tire light. No other lights are on, and I'm not aware of any built-in diagnostics I can run.

Thanks for any help you can think of.

 

[DanMazdaMan]

I'm having a similar issue. The voltage is controlled by the PCM. 2 wires coming from alternator connector (blue and grey) one is signal and other is command. My connector is broken inside (black plastic around pin crumbles). My 2 wires are showing connection between alternator end and pin on fuse box connector (which are not the same color so I'm lost now).
Which tire blew out? Check that the battery indicator light blinks on when you turn key on. With all the issues you have, sounds like driver tire blew.

 

[DanMazdaMan]

P/N S2533 (3 wire connector) first pic.
The one I got all wires are black comes with 3 crimp style connectors for slicing.
Match to old (2 wire connector) second pic.
I put a small wire nut on the used one and taped it up.
They provide a good length of wire on pigtail, but no need to cut old one off very long.
After installed things became interesting.
Worked fine for a few minutes then car died (rpms went below 500).
I checked battery voltage while someone inside turned on everything one by one.
High beams, AC on high, rear defroster, hazards, interior lights, wipers, radio, door open, foot on brake. Worked fine until put in reverse that's when voltage dropped below 12 (8-9 lowest) and it died.
I put a new battery but don't think it helped to be honest. My battery was only 1 1/2 years old but had been jumped/on charger several times. Same thing occured except this time I was inside car and revved engine when put in reverse to keep RPMs up. Brake became very touchy and then suddenly it ran normally.
I noticed every time the battery is disconnected, it takes the car a while to run like it should. First few minutes is normal, but after 5-10.
This was at 1:00 am. At 4am, car was driven about 60 miles round trip and no issues.
Now, my car has had a MAF sensor issue for years and runs a little different than normal.
Check battery cables/terminals for corrosion. Especially negative where it grounds to body next to battery.

 

[rrubel]

Thanks for the responses. I'll spend some time this weekend looking at the grounds and checking the voltage with someone else inside. Terminals are clean; it's a brand-new battery and the car only has ~85k on it.

 

[rrubel]

Ok, it HAS to be alternator or voltage regulator. Any time the car goes under load, it dies. At idle, pop the AC on, the voltage drops from 13.5 to 11. Turn on the rear defroster, it instantly dies. That's not a bad ground... and I can't see problems with the ground wires, but I also couldn't get it up high enough to crawl under, where it's sitting.

 

[rrubel]

Took the car to yet another mechanic. They agreed that it's the alternator (it was painfully obvious) and are replacing it. Sadly, VERY expensive part.