At a glance
Symptoms
- • A continuous, uninterrupted humming noise from the back or bottom of the fridge
- • Noticeably higher monthly electricity bills
- • Excessive heat radiating from the sides or bottom of the refrigerator
- • Food freezing in the fresh food compartment
- • Heavy frost buildup on the rear wall of the freezer
- • The refrigerator struggles to maintain a cold temperature despite running constantly
Common causes
- • Heavily impacted or dirty condenser coils restricting airflow
- • Torn, brittle, or misaligned door gaskets allowing warm air to enter
- • A faulty temperature control thermostat failing to signal the compressor to stop
- • A blocked or failed condenser fan motor
- • Extreme ambient temperatures (especially common in uninsulated garage installations)
- • A sealed system refrigerant leak or failing compressor valves
Safety First — Read Before You Start
- •Always unplug the refrigerator from the wall outlet or flip the dedicated circuit breaker before removing access panels or touching electrical components.
- •Never attempt to tap into, cut, or braze the copper refrigerant lines. Handling refrigerant requires specialized equipment and an EPA 608 certification.
- •Be cautious of sharp, unfinished sheet metal edges when vacuuming around the compressor and condenser coils.
- •When testing the condenser fan, keep your fingers, loose clothing, and hair well clear of the fan blades if the unit must be temporarily plugged in.
Tools & supplies you'll need
- Appliance condenser coil cleaning brush
- Shop vacuum with a narrow crevice attachment
- Digital multimeter
- 1/4-inch nut driver and Phillips screwdriver
- A crisp dollar bill (for testing door gaskets)
- Appliance thermometer
Step-by-step instructions
Assess Ambient Temperature and Clearances
Start by checking the environment surrounding your fridge. If your unit sits in an uninsulated garage in a place like Bend or rural Washington during a heatwave, the ambient air can easily climb past 100°F, forcing the compressor to run nonstop to battle the heat. Also, ensure there is at least 1-2 inches of clearance behind and above the unit for ventilation. Move the fridge away from the wall if it is pushed too tight, and use an appliance thermometer to verify if the interior is hitting the ideal 37°F in the fridge and 0°F in the freezer.
Tip: If your fridge lives in the garage, consider installing a garage kit or upgrading to a model built to handle fluctuating temperatures.
⚠ Warning: Do not attempt to modify the sealed system to 'boost' cooling power in a hot environment; this will destroy the compressor.
Clean the Condenser Coils
Dirty coils are the most frequent cause of constant compressor operation. These coils release the heat pulled from inside your fridge. If they are covered in dust, pet hair, or grime, heat cannot escape. Unplug the appliance and locate the coils, usually found behind the bottom toe-kick or on the back. Use a long, flexible condenser coil brush to loosen the debris, then vacuum it up with a crevice tool. Removing this buildup can improve efficiency by up to 30%.
Tip: In damp coastal regions like Bellingham, dust often turns into a sticky mat on the coils, requiring a stiff brush to clear.
⚠ Warning: Do not use water or liquid cleaners on the condenser coils, as they are located directly next to high-voltage electrical components.
Perform the Dollar Bill Test on Door Gaskets
Leaky gaskets let warm air inside, preventing the fridge from reaching the set temperature and causing the compressor to run forever. Place a dollar bill halfway between the door and the frame and close it. You should feel resistance when you try to pull it out. Test the entire perimeter of both the fridge and freezer doors. If the bill slides out with little effort, your gasket is worn out. You can buy new gaskets for $50-$120 and install them manually.
Tip: If the gasket is merely misshapen, you can soften it with a hairdryer on a low setting and gently smooth it back into shape.
⚠ Warning: Do not use a heat gun to reshape gaskets; it will melt the rubber almost instantly.
Inspect and Test the Condenser Fan Motor
Most modern units include a condenser fan near the compressor to push air over the coils. Unplug the fridge, remove the rear access panel with a 1/4-inch nut driver, and check the fan. Spin it by hand; it should move easily. If it feels stiff, the motor is likely bad. If it spins, you can check it for continuity with a multimeter. A new condenser fan motor typically runs between $40 and $90.
Tip: Sometimes a simple obstruction like a plastic bag or heavy dust clump is blocking the blades—clearing this may fix the issue.
⚠ Warning: The edges of the fan blades can be sharp. Handle them carefully to avoid cracking the plastic or cutting yourself.
Test the Temperature Control Thermostat
If the fridge is running constantly but the interior is too cold (i.e., your produce is freezing), the thermostat might be stuck. Unplug the fridge and reach the thermostat inside the fresh food compartment. Disconnect the wires and use a multimeter set to the lowest Ohms (Rx1) setting. The thermostat should show continuity (0 ohms) at the coldest setting and no continuity in the 'Off' position. If it shows continuity when off, it is faulty and needs replacement ($30-$80).
Tip: Take a photo of the wire connections before unplugging them to ensure you reattach them to the correct terminals on the new thermostat.
⚠ Warning: Ensure the power is disconnected before performing any continuity tests.
Check for Evaporator Frost (Defrost System Failure)
If the compressor runs constantly but the fridge stays warm, inspect the back wall of the freezer. Thick ice buildup suggests a defrost system failure. The ice blocks airflow, forcing the compressor to work overtime. Unplug the unit, remove the rear freezer panel, and inspect the coils. If they are encased in ice, you will need to thaw them and look into replacing the defrost heater or bi-metal thermostat.
Tip: Heavy frost usually points to a failed defrost heater ($40-$80) or defrost bi-metal thermostat ($15-$30).
⚠ Warning: Never use a hair dryer or heat gun to melt ice off the evaporator coils. The plastic liner of the freezer will warp and melt very quickly.
Brand-specific notes
Some brands have known design quirks worth knowing about before you start.
LG
LG refrigerators use a linear compressor that naturally runs more often at a lower speed than traditional compressors. However, if it runs constantly and the fridge is warm, it is a hallmark sign of the notorious LG linear compressor failure, which requires a professional sealed-system repair.
Samsung
Samsung's Twin Cooling system utilizes two separate evaporators and fans. If the fresh food compartment fan fails or freezes over (a very common Samsung quirk), the compressor will run continuously trying to cool the fridge side, even if the freezer is at the correct temperature.
Whirlpool
Many Whirlpool, KitchenAid, and Maytag models have condenser coils located underneath the unit in a tight 'W' or 'Z' shape. These are notoriously difficult to clean and clog easily. You absolutely need a specialized, highly flexible coil brush to clean them properly.
Sub-Zero
Built-in units like Sub-Zero often feature dual compressors (one for the fridge, one for the freezer). The condenser coils are located at the very top behind a flip-up grille. Because they are near the ceiling, they pull in cooking grease and dust, requiring cleaning every 3-6 months to prevent the compressors from overworking.
GE
On certain GE models, the main control board (motherboard) is prone to relay failures. The relay that powers the compressor can fuse in the 'closed' position, sending constant 120V power to the compressor regardless of what the temperature sensors dictate.
What our techs see most often
Across the Pacific Northwest, we see a spike in these calls every summer. Often, it's just a fridge in a garage struggling with high ambient heat and a thick layer of dust on the coils. A good vacuuming usually gets things back to normal.
When to call a professional
- → If you suspect a refrigerant leak (the fridge runs constantly, coils are clean, but the unit is warm).
- → If the compressor itself is clicking loudly, extremely hot to the touch, and failing to start properly.
- → If your refrigerator is a high-end built-in model (like Sub-Zero or Thermador) that requires specialized extraction from custom cabinetry.
- → If multimeter testing points to a failed main control board and you are not comfortable working with printed circuit boards.
- → If the electrical outlet or the home's circuit breaker is tripping repeatedly while the compressor runs.
Refrigerator Maintenance & Replacement Tasks
Step-by-step guides for individual maintenance jobs related to this appliance.
A Guide to Cleaning Refrigerator Condenser Coils
How to Properly Level Your Refrigerator
How to Manually Defrost a Refrigerator or Freezer
DIY Guide: Replacing Your Refrigerator Door Gasket
How to Replace a Refrigerator Water Filter (All Major Brands)
Frequently asked questions
How much does it cost to fix a compressor that runs constantly?
Basic maintenance like coil cleaning costs little more than the price of a brush ($15-$20). Replacing a fan or thermostat usually runs $100-$250 for parts. Professional sealed-system repairs or compressor replacements typically range from $800 to $1,200.
Is it dangerous if my refrigerator runs all the time?
While rarely a fire risk, it is very harmful to the appliance. The compressor will overheat, shortening its lifespan, and your electricity bill will climb noticeably.
Can a bad door seal really cause the compressor to run non-stop?
Yes. Leaking seals allow warm, humid air to enter, preventing the internal sensors from ever signaling that the unit has reached the target temperature.
Why is my garage refrigerator running constantly during the summer?
Refrigerators work best in 60°F-80°F environments. If your garage hits 95°F or higher, the cooling system becomes inefficient, forcing the compressor to run endlessly to maintain safe temperatures.
Related Repair Guides
Troubleshooting a Refrigerator That Won't Cool
A refrigerator that runs but fails to maintain a cold temperature is a common headache for PNW homeowners. Most of these issues stem from clogged condenser coils, a faulty evaporator fan, or a breakdown in the defrost system—many of which can be resolved in under an hour.
Refrigerator Door Not Sealing Properly: How to Fix
A compromised refrigerator seal forces the motor to work harder, driving up utility costs and risking food safety. Discover how to inspect, clean, and install a new gasket to ensure a secure, airtight closure.
A Guide to Cleaning Refrigerator Condenser Coils
Boost your refrigerator's efficiency and head off costly compressor issues by keeping your condenser coils free of debris. This quick 20-minute maintenance task is vital for the health of your appliance.