Testing Your Yanmar Starter

So your starter is acting up and you are not sure what to do next.

The first thing you need to do is be sure the problem is your starter and not something else.
A malfunctioning starter may just be a symptom of another problem. It could be anything from a bad battery connection to a bad ignition switch or bad clutch safety switch. Here are some steps to eliminate some other potential problems.


Things to start with:

  • Is your battery fully charged? Seems obvious but we have to start somewhere right?

  • Do you have good connections at your battery and especially where the ground wire bolts to the frame . This is a common spot for a bad connection. Keep in mind that a bad connection may still allow low current circuits like your headlights to turn on but can still fail with higher draw circuits like your starter. One good test is to turn on your headlights and try to run the starter. If the headlights dim or go out then you have a bad connection or low battery.

  • So your headlights stay strong when you try your starter so now we need to check the actual starter.

  • !!!!!! WARNING !!!!! This step is dangerous so, if in doubt, call a professional. Put your PTO in neutral, put your transmission in neutral, and lower the throttle to the stop position. The LAST thing you want is for your tractor to fire up in gear at full throttle and run over you or someone else.

  • Note the labeling of the terminals in the diagram. Terminal 'A' will be the big terminal that does NOT have the wire going down into the starter motor itself. You can not just go by the position of the terminal! It will not always be on the left, for example. Terminal B is the small plug. Terminal C has the wire that goes down into the starter and terminal A is the terminal that the main battery wire goes to.

  • The main wire from your battery goes to terminal 'A' and from there a smaller wire goes up to the fuse box and the rest of the tractor. If your headlights come on then we know this terminal has power. Terminal 'B' is where the wire from your ignition switch attaches to. It is what tells the solenoid to engage and make the starter motor spin. You are going to touch a screwdriver (or other metal object) from terminal 'A' to the small terminal 'B' (basically fooling the solenoid into thinking it got a signal from the ignition switch to go to work).... (OK.. the solenoid is just a chunk of metal and does not really get 'fooled' but you get the idea... right?). If your starter is working correctly then you should get a small spark and the engine should start to turn over. If so, you know that the problem is NOT the starter and you need to work up stream to find the real problem (safety switch, ignition switch, broken wire, bad connection).

  • If your engine does NOT turn over when touching A to B (and your headlights do not go dim) then there is something wrong with the starter or solenoid. You can touch from terminal 'A' to terminal 'C' and listen for the starter motor to spin (the engine will not turn over though because the starter solenoid did not engage the drive gear into the engine). If the starter motor spins then it might just be a bad starter solenoid. We have both. Just give us a call!