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possible new alternator failure?!

December 20, 2013, 08:43:25 pm

Late this summer I finally broke down & bought a new alternator.  It was an exact replacement and after a lose bolt a few years ago went thru my radiator I made sure to snug up the belts & put lock tight on the  bolts.  For the last four years we've had a none working alternator and ran the generator every place we went, and always had the boost switch on, weather it is right or wrong its always worker. When I put on the new alternator the volt gages was up toward 14 but we hadn't drove it anywhere at that point. Tonight were driving along & noticed my volt meter is really low, like 11, so I watched for a few minutes while driving,  and then hit the boost switch.  With a furance, dash heat, fans & lights on the host switch brought if back up to 12 & everything is running like it should,  with no lag  and remember the generator &boost switch are both on.  When I turn the boost switch back off my volts drop down like it did before the new alternator was installed,  so I assume something has failed.  Currently its 830 pm , we are nearing Ann Arbor Mi & hoping to make it to Cincinnati tonight  & find a parking lot to stay in.  I have not checkd to see if the belts are lose but if they are not what could cause the alternator to fail?

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Re: possible new alternator failure?!

Reply #1 – December 20, 2013, 08:50:59 pm

You could have a broken wire to the alternator, also could have a bad battery isolator. Check all wires at the alternator. If the alternator has 4 wires to it you should have no voltage on the large positive wire with the engine not running, one small wire should have 12 volts running or not and the other small wire should have 12 volts with the ignition on. With the engine running there should be about 14 volts at the large positive wire at the alternator. There is quite a bit of information on this forum about alternators. Good luck

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Re: possible new alternator failure?!

Reply #2 – December 20, 2013, 08:57:35 pm

Thanks Red Tractor - where can I locate the battery isolator & what is the method to test it?

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Re: possible new alternator failure?!

Reply #3 – December 20, 2013, 09:16:54 pm

On your coach, the isolator is behind the left rear wheel mounted on the frame facing out toward you. It is finned about 5 inches by 10 inches with 3 terminals on it. With the engine not running should have no voltage on the center terminal and battery voltage on the end terminals. With the engine running should have 14-14.5 volts on the center terminal and 13-13.5 volts on the end terminals. If further questions call me at 813-215-3463. Ron

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Re: possible new alternator failure?!

Reply #4 – December 20, 2013, 09:22:19 pm

Thanks Ron!  I will be checking it in the morning.

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Re: possible new alternator failure?!

Reply #5 – December 20, 2013, 09:23:20 pm

Call me in the morning. Ron

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