2003 Mazda alternator going bad?

JoeFriday

New member
I just replaced this stinking thing in July. Today I noticed my Tribute was idling very low, between 600-800 rpm. Upon closer inspection I could see the dash lights dimming and returning in brightness every few seconds and I could hear the heater blower speeding up and slowing down. No visible check engine lights have been thrown.

I stuck a volt meter on the battery when I got home and here are the results.
12.7 volts at rest.
With the vehicle running the voltage bounces between 14.25 to 14.45 volts and every 7 seconds it drops to 13.8 then returns.
With a load (heater and lights) it hovers around 14.15 volts and still dips down to 13.8 volts but after longer periods of time. The dip in voltage only lasts a second or so.

The interval of seven seconds is puzzling, maybe its some internal electrical part turning off and on. Tomorrow when it's warmer and I have light I will measure the voltage directly at the alternator but I really don't expect anything different. So is this an alternator about to die?
I forgot to add;
The idle even low is smooth. The lights dimming and weird heater blower speed continued even when I hold the throttle for a higher rpm. Acceleration seems fine.
 
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