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Mazda B2500 Electrical charging system overcharging

braveheart3braveheart3 Posts: 3
edited May 2014 in Mazda

I have a 1999 B2500 that I experiencing electrical charging issues that I cannot determine root cause. I am on my 3nd alt in 5 weeks. The last (new) alt charged 13.5 vlts at idol and 15.5vlts at about 2500 RPM. The alt surface temp goes to around 190 degrees after 15 minuets of driving normal in town.
The first alt just quit charging the battery enough to operate the vehicle.
The second alt failed with a melted main post on the back side at the lead supply cable.
Now 5 days later (with the 3ndalt) the truck just quit running...battery too low to operate the vehicle.

Question: is there something within the electrical system of the vehicle that controls the alt or would cause premature alt failure?

Please advise
Thank you,

Best Answers


  • Thank you for the feedback. I have validated that the battery cables are clean, free of corrosion and secure to the battery post.
    I will verify the battery ground cable to frame and engine ground strap are not compromised by corrosion and that they are securely anchored to the frame and engine.

    Thank you,

  • Thanks. Mr_Shiftright.
    I appreciate your comment regarding internal voltage validates what I thought to be the case.
    You may be on to something regarding an issue in the ignition to alt circuit. Would you have any advice how to perform testing/troublshooting or perhaps how to isolate the cause?

    Thank you,

  • Hi all... new to this site but I must say thank god I found this site. I got a 2001 B2500 with 250K on the dash. About a month ago my 'ole faithful' did want to start up. I disconnected the air intake system and sprayed it with some bug spray and she tumbled right over. Got to the electrician and found that the OCR was blown due to the alt overcharging...12.9V on the battery poles....14.1V on idle....the electrician did some minor soldering to the OCR and sent me on my way. Do I need to change my alt or should I repair my old alt...that's my question.

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