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tractormike

onan electrical question

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tractormike
I have an onan model ms twin cylinder engine I am trying to get the charging system to work on. I have ac current coming from the two wires off of the engine. When I plug those two onto the regulator I get dc current off of the b+ terminal but the dc current seems to be positive ground 12 volts. I have to put the positive probe from my volt meter to ground and the negetive probe on the regulator terminal to read voltage. Is the regulator bad or do you have to polorize something before it works right. All the parts are original, I have not tried a new regulator yet. Thanks in advance for any help! ? Mike

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Dadsy98
Mike, what is the B+ voltage off the regulator? should be around 14~15 volts. If the regulator circuit uses a bridge diode network you might have two diodes shorted. I suppose you could swap connections on the regulator, that is, remove the regulator from the frame, connect the old B+ wire to the shell of the regulator then connect the B+ terminal to the frame (ground). You would then remount the regulator making sure it's isolated from the frame. Sorta crazy I know! just thinking here... Steve

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Dadsy98
How true. Well, since the engine has an alternator and appears okay I'd say the rectifier/regulator is at fault. Probably a $2.00 fix if you could unpot the circuit board. Murphy is present there as well. I did get my rectifier/regulator apart and fixed with a $1.00 zener diode. I figured if I'm tossing it I might as well tear it apart. Steve

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jack1747
Mike, start by hooking everything up the way it should be. You really can't check a regulator without it being connected to the battery. With everything hooked up read the voltage on the b+ terminal with the ignition switch on, an the engine NOT running. Compare this reading to the read you get on the battery terminals. It should be exactly the same (unless you have a real expensive digital meter). If the voltage readings are not the same, stop here an fix your wiring. If the readings are the same start the engine and check the voltage at the b+ terminal it should be higher than before. The voltage reading will depend on the condition of the battery but it will be higher. If it is not higher, the regulator is a good bet. Jack

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tractormike
Thanks for the advice everyone. I finally got time to work on it this afternoon. It was the regulator that was the problem. Put a new one on after checking everything out. Now with everything hooked up I get 14 volts when the engine is running and it is the correct polarity. Thanks again. Mike

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