Lawn Mower Blows Fuse When Starting- Causes and Fixes

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Although changing a blown fuse on your lawn mower is easy, determining the cause of the problem can be a bit challenging. 

Your lawn mower will keep blowing fuses when starting, regardless of how many times you replace it unless you identify the root cause of the problem and take practical steps to fix it.

In this article, I share some common reasons why lawn mowers blow fuse and the steps you can take to fix these problems.

Reasons Why Your Lawn Mower Blows Fuse When Starting

To figure out why your lawn mower blows a fuse when starting, you should take some time to carefully inspect and troubleshoot different parts of your lawn mower’s engine

Some of the reasons the fuse of your lawn mowing machine blows include:

  • A short circuit
  • Defective ignition switch
  • Faulty wiring harness
  • Damaged starter solenoid
  • Problem with the alternator stator
  • Voltage regulator short

Lawn Mower Blows Fuse When Starting: Causes And Fixes

1.  Short Circuit 

Most frequently, the reason a mower blows fuse when starting is a short circuit. This happens when a broken wire or lagging component allows electrical current to travel in an alternate direction to the lawn mower’s metal frame.

As a result, the fuse blows to prevent further wiring damage and fire outbreak.

Fix: 

If this is the situation, the fuse will keep blowing up even after being replaced. To prevent this, you’ll need to find the wire or component that is causing the problem.

This can be done by isolating branches of circuits in the wiring and testing each circuit using a multimeter device. When the faulty wire has been detected, it should immediately be removed and replaced.

You can do this yourself if you have the right skills or contact a lawn mower technician to troubleshoot and fix the faulty component.

2. Defective Ignition switch

A defective internal ignition switch can cause the fuse of your lawn mower to blow when starting. 

If this is the case, the damaged ignition switch should be replaced to prevent further damage.

Steps To Replace Damaged Ignition Switch

  • Disconnect the wire harness that is connected to the back of the ignition switch
  • Release the locking tabs
  • Pull out the ignition switch from the dash
  • Replace the ignition switch with the newly purchased one

When purchasing a new switch, request for the exact size and model of the previous one to prevent damage to your lawn mower engine.

3. Faulty Wiring Harness

A lawn mower has three wire harnesses. One each for the dash, chassis, and engine. A fault in either of them can make the fuse of the lawn mower blow when starting.

Fix:

Check the dash wire harness first. This can be done by unplugging the chassis and engine harness to isolate the dash wire harness. If it is okay, check the engine and chassis wire harnesses respectively. 

The faulty harness should be replaced with a new one when found, or the blue wire of the harness can be fixed if the damage is minimal.

4. Damaged Starter Solenoid 

The solenoid of a lawn mower is situated below the battery. It can be a 3-post or 4-post solenoid. The deterioration of the solenoid or weak terminals can affect the lawn mower and subsequently lead to a blown fuse.

Fix:

To fix this problem, the damaged solenoid should be taken out and replaced with a new one. 

Ensure to purchase an identical type of solenoid. Take note of whether the faulty one was a 3-post or 4-post solenoid.

5. Problem With The Alternator Stator

Your lawn mower’s fuse may blow due to an alternator issue. Your lawn mower’s alternator system is in charge of maintaining the battery’s charge while it is in operation by converting Alternating Current to Direct Current.

The stator, which is made of copper wires, is rapidly spun by the magnet on the rotor to drive the alternator. The magnets of the alternator stator can get broken or cracked causing the electrical system to overload and blow the fuse.

Fix

The damaged stator should be replaced with a new one. Replacing an alternator stator might require some technical experience so you may need to take it to a repair shop or a professional technician to get the work done.

6. Voltage Regulator Short (Faulty Rectifier)

The rectifier of a lawn mower functions as a voltage regulator. The amount of voltage sent to the battery is modified by the voltage regulator. Older mower engines have it as a separate system but modern alternators already have this integrated. 

A voltage regulator short can overload the battery by charging it with too much electricity, breaking a fuse in the process.

Fix:

Open up the lawn mower’s engine and inspect the rectifier. If it is seriously damaged, it is best to purchase a new one to replace it.

Make sure to purchase the right type and model to prevent further damage to the engine.

What To Do If Your Lawn Mower Continuously Blows A Fuse

Here are some of the things you can do if your lawn mower continuously blows a fuse:

  • Check For Overloaded Circuits

When circuits are overloaded, the fuse of the circuit breaker will try to prevent overheating and electrical damage by shutting off. 

To prevent this, check to see that all electrical parts and devices are well connected and working properly. 

  • Confirm The Right Fuse Is Being Used

Fuses come in a wide variety of sizes, shapes, and structures. Despite having identical looks, they often serve different purposes. 

The fuse panel might sustain significant damage if the improper fuse was fitted. Using the wrong fuse type can also cause the fuse to blow continually when the system is ignited.

  • Repair Any Damaged Wiring Or Component

Damaged wiring and electrical components can generate excessive electricity causing the fuse to blow or become damaged. 

A thorough electrical inspection should be carried out to find and replace any wire or element that may have been damaged.

Conclusion

Some of the reasons your lawn mower blows fuse when starting include a short circuit, defective ignition switch, faulty rectifier, etc.

To determine the root cause, carefully examine and troubleshoot the vital parts of your lawn mower’s engine as mentioned in this article. Then, apply the recommended fixes.

If the problem persists, it is best to seek the help of a professional or visit a repair shop to find a solution.