How to Electrically Test Garage Door Safety Sensors?

Rabia Tingat • June 18, 2025

Garage door safety sensors play a vital role in ensuring the safe operation of your automatic garage door. These sensors, often referred to as “electric eyes,” detect any obstruction in the door’s path and prevent it from closing on people, pets, or objects. If your garage door is refusing to close or keeps reversing, it could be a sign that the safety sensors are malfunctioning. One of the most reliable ways to diagnose the problem is through electrical testing. In this article, we’ll walk you through how to electrically test garage door safety sensors, using tools and techniques that are easy to understand—even if you’re not an electrician.


What Are Garage Door Safety Sensors?


Garage door safety sensors are mounted on each side of the door, around 4–6 inches from the ground. They work in pairs—one emits an infrared beam, while the other receives it. If anything interrupts this beam while the door is closing, the system reverses the door’s motion to prevent accidents. However, if these sensors are misaligned, dirty, or faulty, they can send incorrect signals to the garage door opener.


When Should You Test the Sensors Electrically?


While visual inspection and cleaning are good first steps, electrical testing becomes necessary when:


  • The LED lights on the sensors are off or blinking.

  • The garage door won’t close despite proper alignment.

  • You suspect wiring or internal sensor failure.

If cleaning and realigning the sensors don’t solve the problem, it's time to use a multimeter to perform an electrical check.


Tools You’ll Need


To electrically test garage door safety sensors, you’ll need:


  • A digital multimeter (set to DC voltage and resistance settings)

  • Screwdriver (to remove sensor units if needed)

  • A clean cloth (to wipe lenses)

  • Electrical tape (optional, for wire marking)

Step-by-Step Guide to Electrically Test Garage Door Sensors


Step 1: Disconnect Power

Before you begin, always unplug the garage door opener from the power outlet. This ensures your safety while working with electrical components.


Step 2: Inspect Sensor LEDs


Each sensor has an LED light—one usually glows green and the other amber. If either light is off, blinking, or dim, it’s an indicator of misalignment or electrical failure. Make a note of the LED behavior before proceeding.


Step 3: Check the Wiring Connections


Examine the wiring connected to each sensor. Look for loose, corroded, or frayed wires. If the wires are damaged, the sensor may not receive power or signal properly.

If needed, use a screwdriver to remove the sensor covers and access the terminal connections.


Step 4: Use a Multimeter to Check Voltage


Turn on your multimeter and set it to measure DC voltage. Reconnect the power to the garage door opener just for this step.


  • Place the multimeter probes on the terminals where the sensor wires connect (usually red to positive and black to ground).

  • A functioning sensor should read around 5 to 6 volts DC. If there's no reading or a very low one, the sensor may not be receiving power, or the wire is damaged.

After the voltage check, unplug the opener again before proceeding to resistance testing.


Step 5: Test the Sensor Signal


Set your multimeter to measure resistance (ohms). Disconnect the sensor from the wiring harness, then place the probes on the input terminals of the sensor itself.


  • A steady resistance reading suggests the sensor's internal circuit is intact.

  • Infinite resistance or no change on the multimeter may indicate a broken or failed sensor.

If both voltage and resistance readings are abnormal, it’s time to replace the faulty sensor.


Step 6: Check the Sensor Wires


If the sensors seem fine but still don’t work, test the continuity of the wires leading from the sensors to the garage door opener.


  • Disconnect both ends of the wire.

  • Place the multimeter in continuity mode.

  • Touch the probes to each end of the same wire. A beep or low resistance indicates proper continuity; no sound or infinite resistance means the wire is damaged.

What to Do If a Sensor Fails the Electrical Test


If the sensor fails any of these tests, it’s likely defective and should be replaced. Most garage door safety sensors are affordable and widely available online or at home improvement stores. Always replace both sensors as a pair to ensure compatibility and performance.


Final Thoughts


Learning how to electrically test garage door safety sensors can save you time and money while ensuring the continued safety of your garage system. Using a digital multimeter, you can accurately diagnose whether the issue lies in the sensor itself, the wiring, or the power supply. Always start with a visual inspection, clean the lenses, and confirm alignment before diving into electrical tests. If problems persist even after testing and replacement, consulting a garage door technician is the safest next step.

Regularly checking your garage door safety sensors helps prevent accidents and keeps your garage functioning smoothly. With the right approach and tools, even homeowners with basic DIY skills can handle the task confidently.

You might also like

Fix N Go Blog

Why Won’t My Commercial Garage Door Open or Close?
By Rabia Tingat February 16, 2026
Commercial garage door not opening or closing? Learn the most common causes, quick checks, safe fixes, and when to call a pro.
What Size Commercial Garage Door Do I Need?
By Rabia Tingat February 15, 2026
Choosing the right size commercial garage door is one of the most important decisions you’ll make for your building. Whether you’re running a warehouse, auto repair shop, fire station, or retail loading dock, the wrong door size can slow operations, damage vehicles, and lead to expensive modifications later. If you’re asking, “What size commercial garage door do I need?” you’re not alone. Many business owners assume there’s a universal size, but commercial garage doors vary widely depending on use, building layout, and equipment requirements. In this guide, we’ll walk through standard commercial garage door sizes, how to measure properly, and how to choose the right size based on your specific business needs—without overcomplicating things. Why Commercial Garage Door Size Matters Unlike residential doors, commercial garage doors are built for heavy-duty use. They must accommodate larger vehicles, frequent opening cycles, and strict safety standards. Choosing the wrong size can cause daily operational issues, such as vehicles scraping frames or inefficient loading workflows. The correct size ensures: Smooth vehicle entry and exit Safer operations Proper sealing and insulation Long-term durability Essential Maintenance Tips for High-Traffic Commercial Garage Doors Standard Commercial Garage Door Sizes While custom sizing is common, there are several standard commercial garage door sizes used across industries. Most commercial garage doors range from 8 to 14 feet high and 10 to 24 feet wide . However, these are general ranges—not rules. Smaller service bays and workshops often use doors closer to the lower end, while warehouses and loading docks require much larger openings. Common Commercial Garage Door Sizes by Industry Auto Repair Shops and Service Bays: Auto shops typically need doors large enough to accommodate cars, SUVs, and light trucks. A common size is 10 feet wide by 10 feet high , though larger shops may use 12×12 feet doors for added clearance. Warehouses and Distribution Centers: Warehouses require larger doors to accommodate box trucks, forklifts, and pallet movement. Many facilities use doors ranging from 12×14 feet to 18×18 feet . For high-volume logistics operations, even larger custom doors may be necessary. Loading Docks: Loading dock doors are often standardized to align with truck bed heights. A typical commercial overhead door size for loading docks is 8×9 feet or 9×10 feet , depending on dock design and truck types. Fire Stations and Emergency Facilities: Fire stations require tall doors to allow quick exit for emergency vehicles. Common sizes include 14×14 feet or 14×16 feet , ensuring adequate clearance for fire engines and equipment. How to Measure for a Commercial Garage Door Before deciding on a door size, accurate measurements are critical. Measuring incorrectly is one of the most common mistakes businesses make. You’ll need to measure: Width of the opening (side to side) Height of the opening (floor to top) Headroom (space above the opening) Sideroom (space on both sides of the opening) Backroom (depth inside the building) These measurements help determine not only the door size but also the type of door system that will work best. What Size Commercial Garage Door Do I Need for My Vehicles? Vehicle clearance is one of the biggest deciding factors. A good rule is to choose a door that’s at least 2–3 feet taller and wider than your largest vehicle. This extra space reduces the risk of damage and makes daily operations smoother. If your business plans to upgrade vehicles in the future, it’s wise to size up now rather than replace the door later. How Long Do Commercial Garage Doors Last? Door Type Affects Size Requirements The type of commercial garage door you choose can also influence size considerations. Sectional Overhead Doors : These doors open vertically and slide along the ceiling. They’re common and flexible, but they require adequate headroom and backroom. Rolling Steel Doors: Rolling doors coil above the opening, making them ideal for tight spaces. They often work well for wider openings but may have height limitations depending on the coil size. High-Speed Doors : High-speed commercial doors are designed for frequent use and often require precise sizing to maintain performance and safety. Custom vs Standard Commercial Garage Door Sizes If your building doesn’t match standard dimensions, custom sizing may be necessary. Custom doors are common in older buildings, industrial facilities, and specialized operations. While custom doors cost more upfront, they ensure proper fit and long-term efficiency. In many cases, custom sizing is the correct answer to what size commercial garage door do I need. Insulation and Size Considerations Larger doors allow more air transfer, which can impact energy efficiency. If temperature control matters, insulated doors with proper sealing are essential—especially for tall or wide openings. Choosing the right size and insulation together helps control energy costs. Local Building Codes and Regulations Some municipalities have regulations that affect commercial garage door dimensions, especially for fire safety, wind load, and accessibility. Before finalizing your door size, it’s important to check local building codes to avoid costly changes later. Planning for Future Growth One mistake many businesses make is sizing a door only for current needs. If you expect business growth, larger vehicles, or increased traffic, choosing a slightly larger door now can save money and disruption later. Professional Site Assessment Matters While online guides are helpful, a professional site inspection is often the best way to determine the correct size. Experienced installers consider structural support, workflow, and safety—not just measurements. Cost Impact of Door Size Larger commercial garage doors cost more—not just for the door itself, but also for installation, motors, and maintenance. However, choosing a door that’s too small can be even more expensive in the long run due to inefficiency and damage. Conclusion So, what size commercial garage door do I need? The answer depends on your industry, vehicle size, building layout, and future plans. Standard sizes work for many businesses, but custom sizing is often the smartest solution for long-term efficiency and safety. By measuring carefully, understanding your operational needs, and planning ahead, you can choose a commercial garage door that supports your business instead of limiting it. When in doubt, a professional assessment can help you make the right decision the first time. Frequently Asked Questions (FAQ) Q: What is the standard commercial garage door size? A: Standard sizes typically range from 10–24 feet wide and 8–14 feet high , depending on application. Q: How tall should a commercial garage door be? A: The door should be at least 2–3 feet taller than your tallest vehicle or equipment. Q: Can I get a custom-sized commercial garage door? A: Yes, many commercial garage doors are custom-built to fit non-standard openings. Q: Are larger commercial garage doors more expensive? A: Yes, larger doors cost more upfront but often improve efficiency and reduce long-term issues. Q: Should I size my door for future needs? A: Absolutely. Planning for future growth can save significant replacement costs later.
Can Commercial Garage Doors Be Customized?
By Rabia Tingat February 10, 2026
Learn how commercial garage doors can be customized for size, material, insulation, security, and branding to match your business needs.