I helped a friend find a low voltage problem on a newly acquired Steiger 385 just a few days ago. His problem was the battery post crimp on the main cable. But, I do not suggest replacing any parts or wasting any time cleaning various connections until you are able to isolate the problem. And the only way to do that properly is with a voltmeter.

Note: this tractor had the alternator replaced twice in the last 400 hours. Sadly, I think the previous owner threw $800 dollars away replacing perfectly good alternators.

You will need a voltmeter that reads to the tenth (0.1) volt in the range you will be using. You should be able to find one at any auto parts store for about $20.

Start the process by checking your batteries without the engine running. They will most likely be something like 12.6 V. Go to the alternator and check volts between the output post and the alternator frame. It should also be 12.6 volts.

Now start the tractor. Again, check the voltage between the output post and the frame on the alternator. You should see a voltage between 13.5 to 14.5 volts with a good working alternator.

If you do not see any voltage above 13.5 volts, check to see if the excite terminal on the alternator is receiving 12 volts between the terminal and the alternator frame. If it is seeing 12 volts on the excite terminal, then you most likely have an alternator problem.

If you are seeing voltage between 13.5 to 14.5 volts, wait for the voltage to stabilize and note the number. Now go check the voltage on the battery posts (the actual battery posts, not the cable clamps). If this number is 0.3 or more volts lower than your alternator voltage, then you most likely have a connection problem. If you’re A-post is showing 0.3 or more volts lower than your noted alternator voltage, then you most likely have a connection problem. Write back and we will go from there or you can look at these old posts (here and here) to see my recommended course of action.

Mav