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Kevin, Auto Mechanic
Category: Mazda
Satisfied Customers: 2157
Experience:  Diagnostic technician
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Have a 99 Miata battery test as good, tester says bad diode.

Customer Question

Have a 99 Miata battery test as good, tester says bad diode. Just switched out the Alternator with one for my other Miata that I know is good? Any ideas
Submitted: 2 years ago.
Category: Mazda
Expert:  Kevin replied 2 years ago.

Hi im Kevin. Let's start from the beginning what values do you have when idling? Is there any improvement with new alternator?

Customer: replied 2 years ago.
Can not get it started
Customer: replied 2 years ago.
Got it started with a jump and tested the battery, was told the battery was good, but showed a bad diode? Have another Miata that I'm rebuilding the motor in, so took that alternator and switched it out still no start
Expert:  Kevin replied 2 years ago.

Ok once running with multimeter what is voltage at battery?