12 volt alternator discharge

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   My WD45 had been converted to 12 volt sometime in the past. This weekend I noticed that the ampmeter shows discharge when the tractor is running. The battery is brand new and the tractor starts very easily. The alternator has just one wire from a terminal marked "BAT" . There are no other wires to or from the alternator which is different from other alternators I have worked with. I am assuming that the alternator is "self exciting"-no jokes please, and that maybe the ampmeter was wired incorrectly. There is no key start, just an on / off switch and the factory starter rod. Do I need to run a lead from the switched hot side of the switch to the input side of the ampmeter? I did not have my volt meter with me to check output from the alternator.

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WhiskeySup Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 17 Apr 2011 Points: 233	Post Options Post Reply Quote WhiskeySup Report Post Thanks(0) Quote Reply Topic: 12 volt alternator discharge Posted: 16 May 2011 at 3:46pm
	My WD45 had been converted to 12 volt sometime in the past. This weekend I noticed that the ampmeter shows discharge when the tractor is running. The battery is brand new and the tractor starts very easily. The alternator has just one wire from a terminal marked "BAT" . There are no other wires to or from the alternator which is different from other alternators I have worked with. I am assuming that the alternator is "self exciting"-no jokes please, and that maybe the ampmeter was wired incorrectly. There is no key start, just an on / off switch and the factory starter rod. Do I need to run a lead from the switched hot side of the switch to the input side of the ampmeter? I did not have my volt meter with me to check output from the alternator.

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Tedin NE-OH Members Profile Send Private Message Find Members Posts Add to Buddy List Silver Level Joined: 30 Mar 2011 Location: OH Points: 177	Post Options Post Reply Quote Tedin NE-OH Report Post Thanks(0) Quote Reply Posted: 16 May 2011 at 4:21pm
	If the amount of discharg varies with engine speed, suspect ampmeter is wired backwards. Use a volt meter on the battery. If charginging at 1/2 throtle the battery voltage should be 13+ volts.

Brian Jasper co. Ia Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 11 Sep 2009 Location: Prairie City Ia Points: 10508	Post Options Post Reply Quote Brian Jasper co. Ia Report Post Thanks(0) Quote Reply Posted: 16 May 2011 at 5:58pm
	Those 1 wire alternators require some pretty good engine speed to excite. Check it with your volt meter before you decide its not working. A new replacement ammeter I put in my D17D decided to show -15A with no battery or generator from the time I pulled the engine to when I started putting it back together. Could be the meter.
	"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford

Steve in NJ Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Andover, NJ Points: 11788	Post Options Post Reply Quote Steve in NJ Report Post Thanks(0) Quote Reply Posted: 16 May 2011 at 8:26pm
	One wire Alternators are not a good choice for early Tractors. These units need 1200-1400 rpms in order to excite the VR to put the Alt in a charging mode. The problem is, its tough on the early engines to reach high rpms to turn the regulators on. You may have to rev the engine quite high to get it to charge. Depending on the mfr of the Alt, one wire Alts can sometimes be turned into a 3 wire unit by installing the VR plug and installing a circuit from the key switch to send 12V's to the VR. HTH Steve@B&B

Gerald J. Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 12 Sep 2009 Location: Hamilton Co, IA Points: 5636	Post Options Post Reply Quote Gerald J. Report Post Thanks(0) Quote Reply Posted: 16 May 2011 at 9:12pm
	It can help to install the smallest possible diameter pulley on the alternator. I did that on my gas 4020 and it still takes 1600 RPM at the engine to get the alternator started. I should make it a three wire, but I haven't yet. Gerald J.