A friend has a CD28 with a Volvo MD7A engine and a factory alternator. The alternator was hot to the touch with the battery selector switch in the "1" or "2" or "all" position without the engine running. By hot, I mean almost too hot to touch almost to the "Owe I burned myself 1" point, not quite that hot....... He had the alternator rebuilt last week and reinstalled and still with the selector switch in anythin but "Off" the alternator is HOT. The engine is not running, the boat has been sitting at the dock for hours and days. He had the alternator rebuilt because he thought there was a problem and the local engine repair company recommended it. $200 spent on the job.
Can anyone tell me why the alternator would do this ? Is this normal ? Is it a built in feature to keep the alternator free of condensation ? Can there be a wiring problem ? Any similar experiences ?
Remember this only occurs if the selector switch on the battery selector in not in the off position ... Thanks for your comments, the Cape Dory is a great boat.
georgesail@aol.com
Alternator Problem Cape Dory 28' w/Volvo Engine
Moderator: Jim Walsh
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Scott
Re: Alternator Problem Cape Dory 28' w/Volvo Engine
It's time for some troubleshooting. You'll need a multimeter, preferably with a high anperage scale. Obviously, power from the batteries is flowing into the alternator ... and too much power, at that. First make sure the battery polarity is right .. that is to say that the - side of the battery is connected to ground. Then make sure the alternator is correctly connected (I have an MD-7 manual if you don't). Main connections are simple: ground to D-, positive (from starter solenoid) to B+, but there are some jumpers and the charge iduit light conection too. If that's OK, the problem is probably two or more bad diodes or a bad voltage regulator ... both internal to the alternator. Any alternator shop should be able to check these with the alternator removed (by the way, did the shop diagnose the alternator before they rebuilt it? did they find anything wrong?) You can also isolate this with the multi meter. With the field power disconnected, virtually zero current should flow into the stator windings (engine stopped, of course) ... if it does, you have bad diodes. If this is the case, the current could be tens of amps, be careful. With the field connected, a couple of amps should flow into the alternator regulator/rotor circuits. If this doesn't make sense, remove the alternator and have a shop check it out.
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Matt Cawthorne
Re: Alternator Problem Cape Dory 28' w/Volvo Engine
Keith
As I understand alternators, the coils are energized any time the switch is turned on and the voltage regulator senses a need to increase the system voltage. The lower the system voltage the higher the current into the coils. On my CD36 there is a low oil pressure buzzer that goes off every time I leave the key on and the engine is not running. Is it possible that either the switch is bad, allowing the field to stay energized when the engine is off or that the key is being left on?
Matt
mcawthor@bellatlantic.net
As I understand alternators, the coils are energized any time the switch is turned on and the voltage regulator senses a need to increase the system voltage. The lower the system voltage the higher the current into the coils. On my CD36 there is a low oil pressure buzzer that goes off every time I leave the key on and the engine is not running. Is it possible that either the switch is bad, allowing the field to stay energized when the engine is off or that the key is being left on?
Matt
Keith Fawcett wrote: A friend has a CD28 with a Volvo MD7A engine and a factory alternator. The alternator was hot to the touch with the battery selector switch in the "1" or "2" or "all" position without the engine running. By hot, I mean almost too hot to touch almost to the "Owe I burned myself 1" point, not quite that hot....... He had the alternator rebuilt last week and reinstalled and still with the selector switch in anythin but "Off" the alternator is HOT. The engine is not running, the boat has been sitting at the dock for hours and days. He had the alternator rebuilt because he thought there was a problem and the local engine repair company recommended it. $200 spent on the job.
Can anyone tell me why the alternator would do this ? Is this normal ? Is it a built in feature to keep the alternator free of condensation ? Can there be a wiring problem ? Any similar experiences ?
Remember this only occurs if the selector switch on the battery selector in not in the off position ... Thanks for your comments, the Cape Dory is a great boat.
mcawthor@bellatlantic.net