Hi everyone-

My FD has an issue where it loses voltage while driving. For example, just today (on a 15 min drive), she started up readiing 13.6v, but slowly ran down to 13.0v. Then, there was a sudden drop to 11.5v and the charge light came on. That was at the end of the trip, so I parked her. (This voltimeter seems to read 1v or so lower than what's actually at the battery).

I'm thinking this is an alternator issue (battery is new and seems to hold a charge, but I'm interested in any thoughts or similar experiences others may have. Also, if it is the alternator, is there any preferred replacement?

Thanks in advance for your help!

 

If your alternator has never been replaced it's likely that yours is failing. Another possibility is a loose connection but the symptom would likely be a more abrupt "on and off" with that.

 

Yep, alternator failing. Shop around and see what looks good, I don't know of a preferred brand or anything. May also be worth asking Ray Crowe if they have Mazda new or reman alternators.

Dale

 

I agree it's most likely a failing alternator, but your comment above (in bold/italics) is a clue that has me wondering if your wiring is healthy also? A voltage difference of 1V between readings taken right at the positive & negative battery posts and a voltage reading taken elsewhere on the car (i.e. probe the Alternator B+ power output post and the battery's negative terminal with your voltmeter) indicates a significant voltage drop somewhere in the wiring - this could be a loose/corroded battery terminal, bad ground or similar wiring issue. How & where did you probe voltages to get that 1V difference? Taking voltage measurements at the two places I described should get you nearly identical readings if the wiring is healthy. With the engine off, you should be reading around 12.3~12.6V at both locations, indicating a healthy battery & wiring. With the engine running, you should be reading between 13.5~14.5V at both locations, indicating a healthy alternator & wiring.

 

That's a great observation. I don't get much difference between tests at the alternator and at the battery, so I've always just assumed it's an issue with the gauge (perhaps a loose connection), and since I don't really use it all that much, I've just lived with it. But you've a good point. I'll check voltage at other spots to see if there's a wiring issue....

And thanks everyone for your thoughts (and confirmations) so far!