Mazda CX-7 alternator high voltage

Asked by Jul 27, 2017 at 11:56 PM about the 2008 Mazda CX-7 Grand Touring

Question type: Maintenance & Repair

I have replaced battery and alternator and is still generating high voltage
getting higher as accelerating and boiling battery . Anyone know what voltage
should be on the 2 wires between alternator and pcm .? If engine at idle and
all power consumption is on( ac high beams, windshield wipers etc seems to
be just at about 15.5v but as I accelerate it goes up to 18v or more and
already burned the low beam lights. I had alternator tested and was good,
replaced it anyway and still the same.put new battery still the same.  I saw
others with this issue but none came back after they fixed it to confirm what
was wrong.  

1 Answer

2,335

the alt is getting a wrong signal , one big wire goes to the batt. for charging , one smaller wire is the voltage signal so it knows weather to charge or not , the other small wire is the exciter for the regulator , it needs an initial charge to work , a simpler system has 2 wires and gets voltage info from the batt. and wouldn't account for voltage drops from the rest of the system , it's o.k. for a hot rod ., your experience may differ

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