Heating and Air Conditioning
Knoxville
Heating and Air Conditioning in Knoxville

When Your Outdoor Unit Won’t Turn On: A Homeowner’s Guide

Customer’s Situation
One chilly morning in Knoxville, a homeowner discovered that while the indoor thermostat was happily blowing warm air, the outdoor condenser unit sat silently—no fan, no hum, just a thin layer of snow at its top. With the cold settling in, they called HEP for help.

Diagnosis and Resolution
Our HEP technician arrived and quickly determined the system had gone into a high-pressure lockout. The real issue was a clogged evaporator coil that starved airflow, causing pressure to spike and shut the compressor down. The coil was carefully cleaned, debris was cleared, and the system was reset. Moments later, the outdoor fan and compressor sprang back to life—and the house warmed up again.

Why a Clean Coil Matters

A restricted coil forces your HVAC system to work harder. Over time, dust and debris build up on the fins, which leads to:

Reduced airflow and uneven heating or cooling
Higher operating pressure and possible lockouts
Increased energy bills and potential component wear

Keeping your coil clean can prevent unexpected shutdowns and extend the life of your equipment.

This evaporator coil was so dirty that it caused the system to go into high-pressure lockout.

How Technicians Clean an Evaporator Coil

Professional technicians use specialized foaming cleaners and soft brushes to lift away grime without bending the delicate fins. Here’s what that looks like in action:

Foam cleaner loosens dirt for a thorough rinse, restoring proper airflow.

Tip for Homeowners: Schedule coil cleaning at least once a year—ideally before the heating or cooling season kicks into full gear.

Tools Professionals Use to Verify a Healthy System

Beyond visual inspections, HEP technicians rely on diagnostic tools to confirm everything is running within safe limits:

Clamp Meter: Measures the electrical current of the compressor motor
Digital Manifold Gauge: Checks refrigerant pressures (when needed)
Thermostat Testing: Verifies control signals match actual temperatures

For example, measuring the compressor’s amp draw can reveal if it’s struggling to start—a sign you might need a hard-start kit or further inspection.

Using a clamp meter helps ensure the compressor isn’t drawing excessive current.

Homeowner Maintenance Tips

Change Your Air Filter Regularly
A fresh filter prevents dust from reaching the coil and keeps airflow smooth.
Keep the Area Around Your Outdoor Unit Clear
Remove leaves, grass clippings, and snow to allow proper ventilation.
Schedule Annual Tune-Ups
Professional inspections catch small issues—like a dirty coil—before they become emergencies.
Ask About Maintenance Plans
Enrolling in a routine service plan can often reduce or waive travel fees and ensure priority scheduling.

Ready to Stay Comfortable All Year?
If you need expert Heating and Air Conditioning in Knoxville, trust HEP technicians to keep your system in top shape. Regular maintenance and prompt troubleshooting can save you time, money, and stress—so you never face a silent outdoor unit on a cold morning again.