dieselfuelonly said:
Ok, so here is the update. I tested the alternator yesterday and was getting around 30v at the higher RPMs. So I assume the alternator is still good.
What is next in line to test, are there any fuses that might be blown causing the charging system not to work?
I can only relate my experiences with one specific model of Yanmar - YM2220D. The following assumes your configuration is the same as mine and is valid only if that is true.
The charging circuit is very simple. The alternator generates AC power. That power is conducted to the regulator. The regulator's internal solid state devices converts the AC power from the alternator to a regulated, current limited DC power which is routed to the the positive terminal of the battery.
As far as the charging circuit is concerned, that's all there is to it. No external fuses, just two wires from the alternator to the regulator for the AC circuit and one wire from the regulator to the battery for the DC charging current. There are three additional wires from the regulator, but they are not directly involved in the battery charging circuit.
You've verified that the alternator is functional. The next thing to check is whether or not the regulator is producing DC charging current. First, verify the that case of the regulator is properly grounded. With the multimeter set to read resistance (Ohms), measure the resistance between the regulator case and the tractor chassis. It should be zero or a very low value. If there is significant resistance, remove the regulator and clean all points of contact between the regulator case, the mounting bolts and the firewall. Make sure there is good electrical contact (zero or very low resistance) between the regulator and the firewall.
The next step is to measure the DC voltage provided by the regulator. At the starter motor, a large diameter electrical cable is bolted to the forward end of the solenoid. A smaller diameter wire is attached to the same place. The heavy wire is connected to the positive terminal of the battery and provides power to the starter motor. The lighter wire connects to the regulator to allow DC charging current to flow from the regulator to the battery via the heavy wire. Call that light wire the "charging wire"
With engine off, disconnect the charging wire from the starter motor solenoid. Reconnect the heavy gauge wire. Caution: during the next step, make sure the connector on the end of the charging wire does not touch any point on the tractor chassis. You might temporarily wrap it with electrical tape or something similiar. You want to prevent the charging wire shorting to ground.
Start the engine and set it to about 1000 RPM or so. Now, being careful to prevent the charging wire from touching any point on the chassis, measure the DC voltage beween the charging wire and any bare metal on the engine or chassis. You may have to try several different places on the tractor chassis to be sure your multimeter probe is making a good electrical contact. If you can't find any place that gives a reading in about the 12 to 14VDC range, then no charging current is getting to the battery.
If no charging current, trace the charging wire back to the 6 terminal gang connector hanging off the regulator and note which terminal it's connected to. Identify the corresponding wire on the regulator side of the connector. Disconnect the connector and check the voltage from the regulator wire terminal to chassis ground. If you don't have a DC voltage at that point, your regulator is non functional. If you do have the proper voltage at that point, the charging wire is probably broken or there is a dirty/poor connection in the charging wire somewhere between the regulator and the starter solenoid.
Again, if your tractor's electrical configuration is significantly different from that of my YM2220D, then the above is quite likely to be worthless to you.
