Gen 1 CX-9 Alternator Failure

[BLS]

A couple of weeks ago we had an alternator failure at 155000 miles on our 2009 CX-9. Unfortunately this was at night on a trip so had it towed to a AAA shop for repair instead of working on it myself. Symptoms, crazy warning lights on the instruments so my wife pulled off the highway and shutdown.. Belts looked OK and key on voltage was down to 10.4 VDC.

Shop replaced alternator with a Mazda unit and new battery. Wondering if it could have been fixed just by a new voltage regulator or brushes? Anyway MTBF for me was 12 years and 155K miles. Your results may vary.

 

[Bronco Boy]

Wondering if it could have been fixed just by a new voltage regulator or brushes?

It may have been possible, but for a shop, repairing alternators and starters isn't in their vocabulary.

 

[PTguy]

155,000 miles on the alternator bearings...If they weren't going bad, they were on borrowed time. You got your money's worth from the unit.

Why replace the battery? Was it recharged and tested bad? Or just quite old?

A simple test to find if a voltage problem is the battery or the alternator: Charge the battery. Check the voltage. Start the engine and run the engine a bit above idle. If the voltage is now lower than before, the alternator isn't charging the battery, replace the alternator. If the voltage is now higher than before, the alternator is charging but the battery can't hold a charge, replace the battery.

 

[Ben22101]

I’m having a similar problem with my 2011 CX-9. Did the alternator fix your charging system?