Jinma is a Chinese manufacturer that produces tractors and markets them worldwide. Tractors, like cars, require an alternator to provide electricity to run various devices and to charge the battery. Jinma produces three different alternators that are similar in design and produce an output of 14 volts. The main difference is the wattage each alternator is capable of delivering: this varies between 200 and 350 watts. If you find your battery isn't charging correctly or the electrical equipment in your tractor seems to lack power, then use a multimeter to verify that your Jinma alternator is operating properly.
Check the owner's manual for your Jinma tractor to determine the wattage for the alternator. This information will be in the back of the manual in the specifications section.
Put on a pair of protective gloves in case you accidentally touch an electrical component in the tractor. Avoid wearing loose clothing that may get caught in the engine.
Open the engine compartment and locate the battery. Turn on the engine using the ignition key then turn on as many electrical devices as you can. You need to get the alternator to supply as much energy as possible so you can test the alternator properly. Turn on the lights, windshield wipers and the heater fan.
Set a multimeter to read voltage. Place the sensor on the end of the multimeter's red wire onto the positive terminal of the battery. Place the sensor on the end of the multimeter's black wire onto the negative terminal of the battery. The terminals are marked "+" and "-."
Read the voltage output on the multimeter. It should read 14 volts if the alternator is working correctly. Readings between 13.5 and 14.5 are fine; but if the voltage is less than 13 or more than 15, you need to have the problem professionally addressed because either the alternator or the voltage regulator has a fault. Make a note of the output voltage.
Set the multimeter to read amperes. Place the two sensors on the battery terminals as before. Read the amperes on the multimeter. It should read between 15 and 25 amps, depending on the type of Jinma alternator. Make a note of the reading.
Turn off the electrical devices and the engine. Close the engine compartment.
Multiply the voltage you noted earlier by the amperes also noted. This will give you the wattage. For example, if the voltage is 14 and the amperes 25, the wattage is 350 which means the alternator is operating correctly. An alternator that produces 14 volts and 15 amperes has a wattage of 210.
Check your wattage figure against the figure in the specifications part of the manual. If it's within 10 per cent either way, the alternator is fine. If the wattage is outside these parameters, have it independently checked out.