The voltage regulator controls the electrical current coming from your John Deere lawn tractor’s stator so that its battery will be charged with a smooth current that won’t damage it. Thus, it’s critical to test it regularly to verify that it’s in good functioning order and that, if a problem arises, you can address it quickly to prevent more damage to your vehicle.
In general, you can use a voltmeter to test a John Deere voltage regulator with these steps:
- Locate the voltage regulator
- Connect the voltmeter’s black lead to the ground
- Connect the voltmeter’s red lead to the furthest prong
- Transfer the red lead to the middle prong
- Transfer the red lead to the closest prong
In this article, let me discuss how the voltage regulator works and give you more details on the process of testing your John Deere voltage regulator.
5 Steps to Test a John Deere Voltage Regulator

When you test the voltage regulator lawn mower, knowing how to use a voltmeter is required. Now, let’s test the AM102596 John Deere voltage regulator as an example. Here are the steps:
Step 1: Locate the Voltage Regulator
Park your John Deere on a hard and level surface. Then, set its parking brake and remove the key from the ignition. Raise the hood and look for the voltage regulator on the right side of the engine. You can locate the regulator in the little silver box attached to the engine’s side.
Step 2: Connect the Voltmeter’s Black Lead to the Ground
Disconnect the voltage regulator’s plug from the bottom. Then, turn on your voltmeter and set it to the Ohms scale. Look for the ground wire under the bolt that secures the voltage regulator to the engine block. Connect the voltmeter’s black lead to the bolt with the ground wire underneath it. Then, you can find three prongs under the regulator.
Step 3: Connect the Voltmeter’s Red Lead to the Furthest Prong
Connect the voltmeter’s red lead to the prong furthest from the ground. The voltmeter’s reading should be 31.2 M. If that isn’t the result, you should replace the voltage regulator. But continue to the following step if the reading is correct.
Step 4: Transfer the Red Lead to the Middle Prong

Maintain the black lead on the ground while moving the red lead to the middle prong. The voltmeter’s reading should be in the range of 8 to 9 M. If not, the voltage regulator should be replaced. Continue to the following step if the reading is correct.
Step 5: Transfer the Red Lead to the Closest Prong
Still, keep the black lead on the ground and move the red lead to the prong closest to the ground. Examine the results. The voltmeter’s reading should be between 8 and 9 M. If that’s not the case, the voltage regulator will need to be replaced. But if all of these readings are correct and within the standards, your voltage regulator is in good condition.
Bonus Step: Test Through Its Battery
You can also perform a John Deere voltage regulator test through its battery voltage. Here are the steps:
Step 1: Set Up Your Vehicle
Make sure you park your vehicle on a flat, hard surface. Turn the ignition key to “off” and set its parking brake.
Step 2: Load the Battery
Return to the “neutral” position with the foot pedal. Then, raise the tractor’s hood and turn the ignition key one position over to turn on the mower’s headlights without turning the engine over for 15 seconds to put a slight load on the battery.
Step 3: Set and Connect Voltmeter Leads to the Battery
Turn your voltmeter on. Then, set it to the 50 DC scale. Connect the voltmeter’s positive red lead to the battery’s positive (+) terminal. Then, connect the voltmeter’s negative lead to the battery’s negative (-) terminal.

Step 4: Check the Voltmeter Reading
Start your vehicle’s engine and set the throttle to its fastest position. Over five minutes of operation, the battery voltage should remain between a 12.2- and 14.7-volts DC reading.
FAQs
What exactly is John Deere’s voltage regulator (for a lawnmower)?

The voltage regulator of a John Deere lawnmower ensures that the machine’s battery receives a steady, continuous charge. It runs on a 12-volt system to keep its battery charged. To send back to the battery, the stator on top of the engine must generate 14 volts. The 14-volts must first pass via the voltage regulator, which evens out the voltage-current, ensuring that the battery and electrical system are not damaged. (1)
In my example, which is the AM102596, it’s a voltage regulator used on single-cylinder Kohler engines seen on John Deere lawn tractors. The voltage regulator regulates the electrical current flowing from the stator, ensuring that the battery is charged at a steady rate that will not damage it. (2)
Take a look at some of our related articles below.
- Voltage regulator tester
- How to use a multimeter to test voltage of live wires
- How to test a car ground wire with a multimeter
References
(1) electrical system – https://www.britannica.com/technology/electrical-system
(2) lawn – https://extension.umn.edu/lawncare/environmental-benefits-healthy-lawns