This Air Conditioning repair project involved an older rooftop package unit at a residential property in the Las Vegas area. A package unit holds most of the main Heating and Cooling parts inside one large cabinet. The unit sits on the roof and connects directly to the home’s duct system.
The central Air Conditioner was inspected because its Cooling performance needed attention. During the service, the technician found frost forming around part of the evaporator coil and its copper tubing. Ice inside an AC system is not a sign that the unit is making extra cold air. It usually means something is preventing heat from moving through the system correctly.
Fast Affordable Air provides professional AC repair in Las Vegas, Henderson, North Las Vegas, and nearby areas of Clark County. This project shows why a complete diagnosis is important before making changes to a rooftop HVAC unit.
Inspecting the Rooftop Package Unit
The first pictures show the top fan and protective grille. This fan pulls outdoor air across the condenser coil. The condenser coil is the large metal surface that releases heat collected from inside the home.
The technician inspected the fan grille, motor area, wiring, cabinet panels, and surrounding coil. A weak fan motor, damaged blade, blocked coil, or loose electrical connection can cause the Air Conditioner to run poorly.
The full rooftop view also showed the package unit, metal support frame, and duct connection. The duct is the large metal passage that carries cooled air into the home. The technician checked the connection for visible gaps, damage, or loose sections that could allow cooled air to escape.
Checking the Refrigerant Pressures
BlackMax manifold gauges were connected to the unit’s refrigerant service ports. A manifold gauge is a tool that shows the pressure on the low side and high side of the Cooling system.
Refrigerant is the special fluid that moves heat from inside the home to the outdoors. It does not simply create cold air. It absorbs indoor heat at the evaporator coil and releases that heat through the outdoor condenser coil.
Both pressure readings must be considered together. A low reading by itself does not always prove that the system needs more refrigerant. Low airflow, a dirty filter, a weak blower, a blocked coil, or another mechanical problem can also change the pressure readings.
The technician allowed the central AC to operate while watching the gauges. This gave the system time to settle so the readings could be compared with the unit’s operating requirements.
Measuring the Electrical Load
A Fieldpiece SC260 clamp meter was used to measure electrical current. Electrical current is measured in amps. The clamp wraps around one wire and measures how much electricity is passing through it without cutting the wire.
This test helps the technician understand how hard a motor or compressor is working. A compressor is the main pump inside the Air Conditioning system. It moves refrigerant through the coils and tubing.
A motor drawing too many amps may be overheating, struggling, or working against another problem. A reading that is too low may also point to an electrical or mechanical issue. The measured result must be compared with the rating listed on the equipment label.
Finding Frost Around the Evaporator Coil
After opening the service panel, the technician found frost around the copper distributor tubes near the evaporator coil. The evaporator coil is the indoor part of the system that absorbs heat from the air.
The small distributor tubes divide refrigerant and send it through different sections of the coil. When frost forms in this area, the coil temperature has dropped below freezing. Water from the air can then freeze on the tubing and metal fins.
Common causes of a frozen AC coil include
- A dirty or blocked air filter
- Weak airflow from the indoor blower
- Dirt covering the evaporator coil
- A blower motor or electrical problem
- Incorrect refrigerant flow or charge
- A restriction inside the refrigerant system
Adding refrigerant without checking these other conditions could make the problem worse. That is why the pressure test, amperage test, coil inspection, and airflow review were completed as one diagnosis.
Inspecting the Airflow and Duct Connection
The rooftop pictures show the large supply and return duct transition attached to the package unit. These ducts move warm air to the equipment and send cooled air back into the building.
Poor airflow can cause the evaporator coil to become too cold. The refrigerant continues absorbing heat, but not enough warm air passes over the coil. Moisture then begins freezing on the coil and copper lines.
The technician inspected the accessible duct connection and the inside of the equipment cabinet. The service panels also needed to be placed back correctly. Loose panels can allow outdoor air, dust, or hot rooftop air to enter the HVAC system.
Verifying the System After Testing
A frozen coil must be allowed to thaw before final system readings can be trusted. Running the Air Conditioner while the coil is covered with ice can reduce airflow and place added strain on the compressor.
After the coil condition was addressed, the package unit could be operated again while the technician reviewed refrigerant pressures, electrical draw, fan operation, and airflow. The BlackMax gauges and Fieldpiece meter helped provide real measurements instead of guesses.
Homeowners can learn more about these checks on the company’s Air Conditioning tune-up page. Information about preventive service is also available on the AC maintenance page.
Benefits of a Complete Rooftop AC Diagnosis
- Restores stronger airflow through the vents
- Helps the home reach the thermostat setting
- Reduces unnecessary strain on the compressor
- Helps prevent the evaporator coil from freezing again
- Allows the system to remove indoor heat more effectively
- May reduce wasted electricity caused by long Cooling cycles
- Helps find smaller problems before they damage expensive parts
