Question about 1997 Mitsubishi Montero

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Charging voltage is high -- 1997 Montero Sport

When I start the car, the charging voltage is nearly 16 on the meter. It falls to around 15 after a while, but then goes up to nearly 16 again. If I put on a load, such as wipers, lights and heater fan, it will drop to below 15, but doesn't linger at around 14 the way it used to. The problem has started recently.

I imagine that this is the voltage regulator. On this model, can I replace the voltage regulator, or must I replace the entire alternator? I have an alternator from Autozone that is supposed to have a lifetime warranty, but one never knows with suppliers how well warranties are honored.

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  • leojbourne Dec 21, 2008

    The multimeter reading at the battery terminals with engine newly started at fast idle is 15.5 v., which corresponds to the meter reading inside on the dash. When I turned the engine off, the multimeter at the battery read 13 v., diminishing slowly over time, since the interior light was on. After about five minutes it was down to 12.5 v.

    Any thoughts on whether hammering on the alternator might help? If it's a flaky ground, perhaps that might solve it? Else will I need a new alternator?

  • leojbourne Dec 21, 2008

    Thanks for you clarifications. I will measure the voltage on the battery before starting and during starting, and will try to arrange a load test.

  • leojbourne Dec 21, 2008

    Today I cleaned the battery terminals, including unbolting positive terminal assembly and sanding contacts, although I did not disassemble or clean the wire leads at the crimps (would be a lot of trouble if I messed that up). Battery tested 12.3 v. before starting. Car started right up. Inside dashboard meter, which appears to be accurate when compared with a multimeter at the battery, showed a drop to about 10 v during crank. The crank was brisk. Voltage then showed 15.5 v. on the dash meter, confirmed by measurement at the battery. With lights on, defroster on full and wipers on, the voltage dropped to about 14 on the dash. I tried various things just for fun, like draining the battery a little with the lights on and the engine off, then unhooking the negative battery terminal and hooking it up again. As a last try, I ran good jumper cables to a known new, good battery from my battery (other car engine off) and then started my car. Voltage came up at over 15. Looks to me like the voltage regulator. I'll call the Mitsubishi dealer service manager Monday to see what he thinks. I am supposed to have a warranty on the alternater, but it is direct from Autozone, not from the dealer, so I have to figure out how to do the exchange (assuming Autozone honors the warranty, which I will try to check on before I do all this.) I appreciate the advice, and if anyone has any last words of wisdom or other tests I should do, I will try to do themif I have time, before taking the car to the dealer.

  • Mike Butler
    Mike Butler May 11, 2010

    Have you load tested your battery? If the battery is not holding a charge, or is weak, it may cause the voltage regulator to give it all it can to keep it up. Have you taken a voltage reading while trying to start it, (while cranking it over?) to see how low it goes. (sort of like a load test). If you have the opportunity to wait until morning & check voltage before anything turned on, then check the drop when starting, it may tell you if battery is weak, better yet if there is a shop or auto supply place that would do a load test for you, it will confirm between battery & alternator. I just like to eliminate every possibility before spending the big bucks.

  • Mike Butler
    Mike Butler May 11, 2010

    When you say on the meter, do you mean the dash meter or have you tried with a multimeter at the battery? If not try it with another meter externally to confirm that the dash one is correct. Your probably using all those accessories more now than before too, yes, no?


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Yup, sounds like alternator will need replace, due to regulator defective. Good Luck.

Posted on Dec 21, 2008

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Well, the standart rating for the alternator charging is13 t014.5. any number over that number is cal"over charge" and can damage your batterie or other electronics components

Posted on Dec 21, 2008

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