Mazda Repair: 2001 MPV Alternator light, napa auto parts, defective alternator

Question
Hi John,

I have a 2001 mpv that started flashing the alternator light the other night.  I replaced the alternator about 3 months ago.  The battery tested bad, so I replaced it.  The next day the light came on again.  I checked the battery and the alternator (normal and under load) and they both appear good.  I haven't had any sqealing from the belts.  It appears to come on when under a heavy load, a/c on and under acceleration.  Shut off the a/c and the light turns off.  But it will also come on when accelerating without the a/c.  Can you tell me where the indicator marks should be on the auto tensioner?  I am wondering if the belt has stretched enough that it is loose.

Thanks,
Scott

Answer
The autotensioner needs to be at least at the half way mark on its indicator. A defective alternator may also be suspect as without using a computer analyzing tester it is impossible to localize the issue. NAPA auto parts typically have a tester at there disposal made by Miditronics. It is quite adept at sniffing out charging problems and finding underlying problems that the traditional load testers just cannot isolate. I suggest that you get your local NAPA to test the charging system as purchasing the tester "$1000-$1300 depending on options" is out of the question unless you plan to open a shop. The fact that it is receptive to changing loads indicates that it is defiantly a problem with ether the alternators regulator or the drive system, but the tester may find other problems that are magnifying the problem.

Regards,

John