A dimmer switch allows you to adjust the brightness of the lights in your home. It works by reducing the voltage going to the light bulb. This allows you to create the perfect ambiance whether you need bright task lighting or a dim romantic glow. While dimmer switches are very convenient and user-friendly, they can sometimes stop working properly. Diagnosing the underlying cause of a malfunctioning dimmer switch simply takes understanding a few key things about how they operate. We’ll walk through the most common reasons a dimmer switch may fail and what you can do to get it working again.
Page Contents
Wiring Issues
One of the most common reasons a dimmer switch stops working correctly is an issue with the wiring. Dimmers have very specific wiring requirements that ordinary switches do not. Getting the wiring wrong can lead to the dimmer malfunctioning or only partially working. There are a few key wiring issues that crop up:
Not Enough Wires
Most dimmer switches require a neutral wire in addition to the hot wire that powers the circuit. The neutral wire allows a path for electricity to complete the circuit. Without it, the dimmer won’t function properly. Trying to operate a dimmer without a neutral can result in no lights, flickering lights, or the lights turning off when dimmed.
Wrong Wire Connections
Even when the correct wires are present, they need to be connected properly. The hot and neutral wires must be connected to the corresponding hot and neutral terminals on the dimmer. Grounds wires should be attached to the grounding terminal. If the hot and neutral are swapped, the dimmer won’t work correctly.
Too Many Wires
Sometimes there are too many wires stuffed into the switch box. This can cause wires to short out against each other or the box itself. With dimmers, it’s important not to have too many wires in the box. This prevents wires touching accidentally and allows room for ventilation to prevent overheating.
Bad Wire Connection
Loose wire connections are another wiring issue that can lead to a malfunctioning dimmer. The wires have to be securely connected to the dimmer terminals for proper contact. Loose connections can lead to flickering or intermittent operation as the circuit makes and breaks contact. This intermittent connection produces excess heat that can damage the dimmer.
Dimmer Switch Compatibility Issues
Dimmer switches are not universally compatible with all light bulbs and fixtures. Using an incompatible dimmer is one of the most common reasons for failure. There are a few key compatibility issues:
Wrong Bulb Type
Standard dimmers are designed for incandescent or halogen bulbs. Using them with LED, CFL, fluorescent, or other bulb types can lead to poor performance, flickering, buzzing from the fixtures, and bulb failure. These bulbs require a dimmer switch designed for low-wattage lighting.
Too Many Bulbs
A dimmer switch is rated for a certain maximum wattage it can handle. Hooking up too many light bulbs can overload the dimmer switch circuitry leading to failure. Always check the maximum wattage rating and don’t exceed it.
Incompatible Fixtures
Some fixtures, particularly fluorescent lighting, cannot be controlled by a standard dimmer. Fluorescent lights require a special 0-10V fluorescent dimmer. Using a standard incandescent dimmer will damage the bulbs and ballasts.
Old, Damaged, or Improper Dimmer Switch
Sometimes a dimmer switch fails simply because it is damaged, worn out, or the wrong specification. Here are some ways the actual dimmer can cause operation issues:
Worn Out Dimmer
Like any electronic device containing mechanical, moving parts, dimmers wear out over time. A very old dimmer can simply stop operating properly due to component degradation over decades of use. Average life expectancy for a quality dimmer is about 20 years.
Improper Dimmer Rating
Using a dimmer rated for a lower wattage than the lighting circuit tries to draw will overload the dimmer. Choose a dimmer switch rated for at least the total wattage of all bulbs. Too low a rating will lead to failure.
Corroded or Damaged Contacts
Internal corrosion or damage to a dimmer’s copper contacts can prevent proper operation. Damage is often caused by frequent arcing as the contacts engage and disengage. Arcing creates heat buildup as well.
Moisture Damage
Exposing dimmers to moisture through leaking roofs, condensation, or wet locations can short out vital components. Only use dimmers approved for damp locations in susceptible areas.
Power Surges
Power surges, spikes, and lightning strikes are hard on any electronic device. Surges can damage or degrade sensitive dimmer components leading to failure.
Manufacturing Defect
Some dimmer switches are simply defective right out of the box. Reputable manufacturers replace a defective dimmer under warranty. Try a brand new unit to rule out a manufacturing flaw.
Troubleshooting Steps
If your dimmer switch fails to work properly, there are some troubleshooting steps you can take:
Check Wire Connections
Examine all the wire connections to make sure hot, neutral, and ground wires are securely attached to the proper terminals. Loose wires and incorrect connections are common causes of issues.
Inspect for Damage
Open the dimmer switch and check for any signs of internal damage from moisture, surges, or overheating. Damaged parts like contacts may need replacement.
Test for Correct Voltage
Use a voltage tester to confirm 120V power coming to the switch and leaving the switch when on. No power could indicate a tripped breaker or wiring problem. Low voltage can make dimmers malfunction.
Replace Bulbs
Try swapping incompatible CFL or LED bulbs with standard incandescent bulbs. If the dimmer works properly with incandescent bulbs, the issue is incompatibility.
Test Dimmer with Different Lights
Hook the dimmer up to a table lamp or other lights. If it works fine, then the issue may be incompatible fixtures on the original circuit only.
Eliminate Load
Disconnect all lights to test the dimmer with no load. If it functions properly with nothing connected, the issue is with overload, too many bulbs, or compatibility.
Replace Dimmer
If you’ve exhausted other options, replace the dimmer with a new unit that matches the bulbs and fixtures on the circuit. Only use dimmers approved for LEDs with LED lighting.
Preventing Future Dimmer Switch Failure
Once you’ve solved an issue with a malfunctioning dimmer, take steps to prevent future failure:
Choose Compatible Dimmers
Always check that the dimmer switch is made for the type of lighting on the circuit, be it LED, incandescent, fluorescent, etc. Don’t mix incompatible dimmers and bulbs.
Allow Airflow Around Dimmers
Ensure dimmer switches have room to breathe and dissipate heat. Don’t cram wiring and boxes tightly around dimmers.
Use Surge Protectors
Install surge protector strips and suppressors to protect delicate dimmer switch electronics from power spikes.
Hire an Electrician
If you’re uncomfortable working with house wiring, have a qualified electrician install and troubleshoot the dimmer switch. Following codes and making proper connections will prevent issues.
Check Ratings
Make sure the dimmer switch wattage rating exceeds the total watts of all bulbs on the circuit. Too low a rating risks overheating and failure.
Keep Connections Dry
Prevent moisture damage to dimmer switches by fixing leaks, avoiding condensation, and using outdoor/damp rated dimmers in bathrooms, basements, and wet locations.
Conclusion
Dimmer switches enhance lighting in any room when operating properly, but can fail in frustrating fashion. Burned out bulbs are usually the culprit for lights not responding to a dimmer, but when the dimmer itself malfunctions, there are several wiring, compatibility, and component issues that tend to crop up. Checking for loose wires, overloaded circuits, and inappropriate bulb types covers many common problems. In the process of troubleshooting, you may need to replace damaged dimmer switches if they exhibit any signs of failure. Using the proper dimmer for the lighting load and protecting from surges and moisture will minimize headaches down the road. With some diligence, a failed dimmer switch usually reveals what’s wrong in relatively short order.
| Cause of Dimmer Failure | Solution |
|---|---|
| Missing or incorrect wiring | Check wiring connections and ensure neutral wire present |
| Overloaded circuit | Reduce number of bulbs to dimmer’s rating |
| Incompatible bulbs | Replace with supported bulb types |
| Damaged, old, or wrong dimmer | Replace dimmer with properly rated model |
| Moisture damage | Repair leaks and install damp-rated dimmer |
| Power surges | Install surge protection |
| Dimmer Location | Potential Issues |
|---|---|
| Bathroom | Moisture damage |
| Basement | Condensation, moisture damage |
| Outdoors | Weather damage, corrosion |
| Areas prone to leaks/flooding | Water exposure hazard |
| Fluorescent fixture circuits | Incompatibility with standard dimmers |