Tractor Mechanic

As a graduate of Auburn University, people believe I should know how to repair a tractor. Unfortunately I never took an AG classes so I missed out on John Deere Repair 101.

My neighbor asked me to take a look a this tractor (a YANMAR 1500) with him. The first symptom was a dead battery. Sometimes a dead battery is just a dead battery. Other times it is a problem with part of the electrical system. In this case, the problem was not just the battery. After doing some research online, I took some voltage measurements on the tractor. Based on the numbers, it appeared the alternator was generating sufficient voltage but the regulator was not working. We replaced the regulator but things were still no go. At this point the alternators output had dropped from about 18 volts to about 9. This was a bit of a mystery to me. The best I can figure out, the regulator input was "open" so alternator appeared to be working. Once the regulator was replaced, it put a load on the alternator causing the alternators output under load to drop to 9 volts.

What are the odds both the alternator and the regulator were bad? Not very high if you ask me, but the original symptoms pointed to the regulator not the alternator. Obviously now, the alternator is the problem. Hopefully we will get Coy's tractor running again this week. And then I can take it out for a test drive.