PROBLEM - In the attached wiring diagram the 3 Amp Diode coming from the 28VAC alternator/stator winding burned out and was replaced with the exact type as the old one. After a minute of run time the new Diode gets hot enough to melt it's solder connections.
As you can see, the stator has only two wires coming from it and with the engine running I get 14VAC and 28-30VAC at their respective stator windings. When I attach a common 12 volt 3 Amp tail-light bulb to the 14VAC it lights up as bright as it would be expected. I quickly tapped the same bulb to the 28VAC and it also (but brightly) lit up so I know the stator is working since it has the correct voltage and has no problem supplying current on demand.
Without going into detail explaining all the tests, fixing bad grounds, and hours I've gone through I finally decided to isolate the 28VAC circuit entirely by disconnecting the positive battery terminal so nothing in the tractor would be drawing current. I had to use a small battery to keep the fuel shutoff valve energized and also removed the stator brake circuit, both relays and jumped the seat switch so the engine would run after the start sequence.
So, the "charge" circuit now goes like this.... The 28VAC alternator lead is connected to the anode of a 3 Amp Diode. The cathode connects to one wire of a current meter and the other wire of the meter connects to the positive terminal of the battery.
I momentarily connect the +battery cable to the +battery terminal to start the engine, then remove it so only the cathode of the diode remains connected to the +battery terminal. My current meter shows a 6 Amp current draw at idle and 9 Amp at mid range continuous. Understand there is nothing else connected to that battery. Suspecting a battery that may be shorted or a positive terminal having some current leakage from its case to ground, I replaced it with a working fully charged battery from another tractor and got the exact same result. That diode could boil water and the battery is the only load.
I'm using a silicon diode and observe a forward voltage drop close to .7V. (Vr is 50 and Io is 3.0)
What am I missing? Is there some resistive current limiting wire that I'm unaware of on this tractor?
View attachment 43952
As you can see, the stator has only two wires coming from it and with the engine running I get 14VAC and 28-30VAC at their respective stator windings. When I attach a common 12 volt 3 Amp tail-light bulb to the 14VAC it lights up as bright as it would be expected. I quickly tapped the same bulb to the 28VAC and it also (but brightly) lit up so I know the stator is working since it has the correct voltage and has no problem supplying current on demand.
Without going into detail explaining all the tests, fixing bad grounds, and hours I've gone through I finally decided to isolate the 28VAC circuit entirely by disconnecting the positive battery terminal so nothing in the tractor would be drawing current. I had to use a small battery to keep the fuel shutoff valve energized and also removed the stator brake circuit, both relays and jumped the seat switch so the engine would run after the start sequence.
So, the "charge" circuit now goes like this.... The 28VAC alternator lead is connected to the anode of a 3 Amp Diode. The cathode connects to one wire of a current meter and the other wire of the meter connects to the positive terminal of the battery.
I momentarily connect the +battery cable to the +battery terminal to start the engine, then remove it so only the cathode of the diode remains connected to the +battery terminal. My current meter shows a 6 Amp current draw at idle and 9 Amp at mid range continuous. Understand there is nothing else connected to that battery. Suspecting a battery that may be shorted or a positive terminal having some current leakage from its case to ground, I replaced it with a working fully charged battery from another tractor and got the exact same result. That diode could boil water and the battery is the only load.
I'm using a silicon diode and observe a forward voltage drop close to .7V. (Vr is 50 and Io is 3.0)
What am I missing? Is there some resistive current limiting wire that I'm unaware of on this tractor?
View attachment 43952