ATVs work like dogs and traveling over rough challenging terrain is all in their job description. And it isn’t very surprising when small issues crop up. That said if your ATV does a ton of night work, no lights isn’t a small problem.
An ATV without lights is a serious safety issue and is therefore useless come nightfall, but the good news is – broken lights are usually easy to fix. I’m a mechanic for over twenty-five years and you are in the correct place, very shortly we’ll get this figured out.
The most common causes of non-functioning ATV lights include:
- Blown bulbs
- Blown fuses
- Loose wiring
- Corroded light fittings
In this post, you’ll learn how to diagnose why your lights don’t work and you’ll learn how to fix them right now.
Diagnosing Non-functioning ATV Lights
As a mechanic, I’ve been trained to begin my diagnosis at the very beginning and that means checking a fact is a fact. And the reason I do this is that very often a perceived problem isn’t actually a problem at all.
So what do I mean? Well in some cases a customer may complain about a particular function of their equipment thinking it’s non-functioning only to discover that it does function only not in the way they had thought.
Now I know that’s likely not the case here, especially if you are familiar with the machine.
But if you’re not familiar with your ATV, stop and check an owner’s manual or online for correct operation. Lights generally don’t work as you know unless ignition in position two or bike running but it is possible for your model to have an override switch.
Checking the basics
Your ATV lights may not work for several reasons, but there are a few common causes that are easy to check and so that’s what we’ll take care of here early in the game. This is more of a visual check and you likely won’t need any tools save maybe a good led inspection light.
Go ahead and visually check for the following:
Fuses – The lights are fused and as you know a blown fuse will prevent voltage from reaching the light bulbs. Replacing the fuse is an easy fix and will only take minutes. The fuses are located behind the dash panel and under the seat. They will be marked and the fuse size is important (10 amp usually). A duse that blows shortly after replacing or right away suggests a short in the circuit. More on this below.
Relays – If your ATV has a light relay fitted, (most will) check it operates. A relay clicks when the headlights are turned on. You’ll hear the audible click of the relay as you manipulate the switch from low to high beam. A click sound is a sign the wiring is in good order and the relay is doing its job. That said, it is possible for a relay to click and still be faulty. Relays are typically universal and you’ll often find a second relay on an ATV you can swap out for testing purposes.
Loose Wiring – Loose wiring is common, either loose at the light fitting or at the main block connector. Run a visual check at the rear of the light fittings follow the wiring back and check any connectors that are visible.
Bulbs – Now it’s time to remove and check a bulb. Most are easy to remove, for headlight bulbs remove the terminal connector then the rubber boot, unhook the clip and remove the bulb. Avoid touching the glass of the bulb. That leaves grease residue on the bulb and shortens their life, assuming it’s still good. To identify a blown bulb hold it by the fitting and check to see if the filament is intact.
Checking power and ground
As you know, voltage travels in a circuit. It originates at the battery positive (+)(Anode) and it naturally seeks the shortest path back to the battery, the negative (-)(Cathode) side of the battery. The negative side of the battery is connected to all the metal components of the engine and chassis and is therefore referred to as the ground side of the circuit.
In any event, ATV circuits manipulate this natural flow of energy by passing the available energy across a light bulb and putting some of its potential to work.
When troubleshooting electrical faults, it is common to check for power in the circuit and also for good grounds. One or other side of a problem circuit is at fault. To run these tests we don’t need anything sophisticated, a simple test light will do the job. Of course, a DVOM works great too or a power probe would be magic.
If the circuit is broken or the energy finds a shorter path to the ground and doesn’t pass across the bulb, then the bulb won’t light. This is known as a short and is commonly associated with a fuse that continuously blows when replaced.
Checking which side of the circuit is at fault
We’ll first check for power and then we’ll check for ground at the light fitting block connector itself. For this test, we’ll use a simple test light.
Power side circuit test
The test is as follows:
- Ignition switch in position two (“On”)
- Place the test light crocodile clamp on negative (-) battery terminal
- Remove the light block connector
- Using the test probe, check for power at the connector
If there’s no power at the light connector, check the midpoint of the circuit. In our circuit here, that would be the fuse. Checking the midpoint points us in a direction. ie forward of the fuse, or backward towards the battery.
I like to test where ever is easy to access. No point in stripping covers until we locate the general problem area.
If the powers side of the circuit tested OK, then we’ll need to check the ground side and that’s what we’ll do next.
Ground side circuit test
To test the ground side of the circuit, follow these steps:
- Ignition switch in position two (“On”)
- Place test light crocodile clamp on the positive (+) battery terminal
- Remove headlamp block connector
- Probe block connector (test light, lights up if ground is good)
- Check battery to chassis and chassis to engine ground straps.
Be sure to check battery terminals are tight, clean, and in good order free from broken wires or corrosion. Check the battery to the chassis terminal and the chassis to the engine terminal. They must be free from corrosion or broken wires and the terminals must be tight.
The ground side test is similar to the power side test, but bear in mind, it’s the chassis that provides the complete circuit back to the battery negative. So we’ll need to pay particular attention to ground strap connections.
Common ATV Wiring Faults
Here’s a shortlist of ATV light circuit problem areas.
- Broken wiring at the steering
- Corrosion at light block connectors
- Bad grounds
- Corroded wiring
- Corroded wiring block connectors
- High resistance in block connectors
- Corrosion in relay connector
- Broken ground straps
Replacing Light Bulbs
Replacing bulbs is easy, below outlines the replacement process for a headlamp bulb. A tail light bulb may require a screwdriver as the outer cover is commonly removed to access the bulb.
When fitting bulbs, it’s important to avoid touching the new bulb glass and it’s super important the covers are fitted securely so as to prevent moisture and bugs. If moisture gets in the bulbs will blow prematurely.
Headlamp bulb replacement process as follows:
- Remove the block terminal
- Remove rubber light cover
- Release spring clip
- Remove and discard the old bulb
- Refit new bulb – Don’t touch the bulb glass
- Refit the clip
- Fit the rubber cover
- Refit block connector
- Check light operation
- Check light beam and adjust if necessary
Check and adjust the light beam as necessary – You’ll find a screw adjuster at the rear or front of each light.
The adjuster screw either lifts the beam upwards or downwards.
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John Cunningham is a technical writer here at ATVfixed.com. He’s a Red Seal Qualified Service Technician with over twenty-five years experience. He’s worked on all types of mechanical equipment, from cars and trucks to ATVs and Dirt bikes.