How to Test the Voltage Regulator on a Lawnmower, step by step


Lawnmowers are mechanical devices that require care and frequent maintenance. Right before a scheduled mowing session, witnessing your lawnmower not starting up might be the result of several causes. One such cause is the failure of electrical components in a mower that includes the battery, alternator, and voltage regulator. In most cases, the voltage regulator is the component that is at fault even when the battery is working correctly. In this blog post, we shall provide you with a comprehensive testing procedure that will increase your knowledge about your mower’s electrical components and help solve your problem.

How to test the voltage regulator on a lawnmower through the mower’s battery, step by step:

  • Step 1: With the ignition key removed, connect the battery terminals to the respective multimeter ends and note the reading. A 12V or higher value indicates that the battery is operating correctly.
  • Step 2: Start your mower’s engine at full throttle and note the change in the multimeter’s voltage reading.
  • Step 3: If no change in voltage is observed, then the voltage regulator is probably at fault. A change in voltage shows that the regulator is working correctly.

How to test the voltage regulator on a lawnmower directly, step by step:

  • Step 1: Connect the voltage regulator to the multimeter ends.
  • Step 2: Start your engine and note the voltage reading. No reading indicates the alternator is not working correctly.
  • Step 3: Run the engine at full throttle. A constant multimeter reading indicates that the voltage regulator is operating correctly.

In lawnmowers, the battery provides current to the ignition coil and powers some electrical components like headlights. Most engines utilize a stator, also known as an alternator, to charge the battery while the engine is running. Note that the battery operates at DC while the alternator gives a varying AC supply. This is where the voltage regulator comes into effect. Not only does it convert the AC supply into DC, but it also ensures that the battery gets a constant DC output, which enables it to get fully charged.

This blog will give you useful self-maintenance tips in addition to some frequently asked questions related to the electrical system of your lawnmower.

Testing the Voltage Regulator on a Lawnmower:

● Needed Equipment:

For testing a voltage regulator, you need a portable multimeter/voltmeter. Furthermore, you also need a pair of nose pliers and a wrench set if any bolts are needed to be removed. If your voltage regulator is faulty, you might need a new regulator of the same model for replacement.

There can be two main approaches for testing a voltage regulator on a lawnmower. Both the approaches are authentic. We shall discuss these separately.

● Method 1: Testing via battery:

The detailed procedure is as follows:

– Step 1: Take the safety measures:

You should proceed by parking your lawnmower on a flat surface and setting up the parking brakes. You should make sure that you are wearing safety gloves since you’ll deal with the battery with a voltage across its terminals. Make sure that the ignition key is removed from the switch.

– Step 2: Connect the terminals to the multimeter:

A portable multimeter can be used for this operation. To begin with, connect the positive terminal of the battery with the positive lead of the multimeter. Similarly, connect the battery’s negative to the voltmeter’s negative lead.

– Step 3: Insert the key and add some load on the battery:

For riding mowers, insert the ignition key in the switch and turn it to the first stage so that the mower headlights can be turned on. Now, your voltmeter settings should be on DC volts since the battery provides a direct current. Note the reading displayed by the voltmeter. The value is typically around 12 volts.

Note: If the battery gives this reading, it is charged and in perfect working condition. This reading is also an indicator that you don’t need to change your battery if you face a problem with your mower’s electrical system.

– Step 4: Start your engine and push the throttle:

Now, turn the ignition key and start your mower’s engine. Increase the engine load by moving the throttle arm to the ‘fast’ position. This step increases the alternator’s RPM, thus providing more voltage to charge the battery.

– Step 5: Note the voltmeter’s reading change:

With your engine cranked up, again connect the voltmeter to the battery terminals and measure the DC voltage output. The value this time shall be higher than it was in the case when the engine was off.

Test result: If the voltage shows an increase from the initial value after the engine RPMS goes up, it shows that the regulator and the alternator are operating correctly. Hence, there’s no need for a replacement. However, if no change in voltage value is observed, it shows that the battery uses its voltage, and the fault lies either in the alternator or in the voltage regulator. Therefore, we shall proceed to the next step, i.e., testing the voltage regulator itself.

● Method 2: Testing the voltage regulator circuit:

Now that we know the battery is in perfect condition, the fault lies either in the voltage regulator or the alternator. Let’s investigate this using the procedure given below:

– Step 1: Connect the multimeter to the voltage regulator:

Make sure your engine is turned off at the moment, and the key is removed. First, locate the voltage regulator on your lawnmower. It is generally present just before the battery and after the alternator in the same circuit. Now, attach the multimeter’s terminals onto the respective terminals of the voltage regulator.

– Step 2: Turn the headlights on:

Set the multimeter to measure the DC volts. Next, insert the key and turn the ignition switch to the first level to turn on the headlight. This step adds resistance to the circuit.

– Step 3: Note the multimeter reading:

With the headlight turned on, measure the reading displayed by your multimeter in DC volts. If no reading is displayed, it means that the alternator is not working.

– Step 4: Start your mower’s engine:

Start your engine and push the throttle to the highest setting. Measure the voltage output at the regulator and the alternator separately.

– Step 5: Check your test Result:

Alternator: If the alternator output does not display any voltage reading, then there lies a fault in the alternator. While it is still running, press on its brushes to see if you get any reading now. If you do, you need to replace the alternator brushes, and you are good to go.

Voltage regulator: The voltage regulator, if working correctly, shall display a DV voltage around 14V. Note that it provides a constant DC output that doesn’t vary with time. If the value changes with time or no voltage reading are displayed on the multimeter, you should consider replacing the voltage regulator. They are not much expensive and are readily available from any spare parts dealer.

Related Questions:

1. How can you tell if a voltage regulator is bad?

The most common symptom of a faulty voltage regulator is a dead battery (that has run out of its volts). Furthermore, dim or flickering headlights, engine running erratically or not running at all, and growing corrosion around battery terminals are also the signs that can tell a voltage regulator needs replacement.

2. What would cause a voltage regulator to fail?

Faulty diodes can fail voltage regulators. These diodes convert the alternator’s AC supply to a DC voltage. The current from the alternator flows through six diodes and the rectifier assembly until it reaches the battery. The diodes don’t burn out under typical loads. However, excessive mowing and unnecessary use of headlights can cause these diodes to burn out.

If only a few diodes have failed, the alternator might still drive the electrical circuit by charging the battery. Nevertheless, running your battery in this condition can decrease its life overtime when it’s never fully charged.

3. How long can you work with a bad voltage regulator?

It’s typically around a day until your battery runs out of charge. A bad voltage regulator means that the alternator cannot fully charge the battery. Hence, it won’t be long enough when your engine doesn’t start until you would have to replace the voltage regulator.

4. How long does a voltage regulator last?

Typically, the voltage regulator lasts about the lifetime of your lawnmower or any vehicle. However, just like any other electrical component, it might begin to show signs of damage after prolonged use. The regulators are vulnerable to damage when the battery powers unnecessary electrical equipment. So, for starters, you should avoid overloading your battery and using headlights on your mower.

Final Comments:

Being a homeowner, it is always better to know some common lawnmower issues and their possible solutions. Being knowledgeable helps you solve problems on your own instead of taking the trouble of going to a mechanic. The procedure for testing a voltage regulator is relatively straightforward. However, care must be exercised whenever you are dealing with electrical components like batteries. It is better not to touch the terminals with bare hands or use rubber gloves while you do so. Always make sure you keep your lawnmower well maintained so that its service life is enhanced.

Recent Posts