An Air Conditioner can blow cool air and still have a problem hiding inside it. That is why a complete diagnostic visit involves more than placing a hand near a vent. The technician needs to check temperatures, electrical parts, airflow, and the amount of electricity the system is using.
During this recent air conditioning project, the technician checked a central AC system using a General Tools infrared thermometer and a Fieldpiece SC440 electrical meter. The service also included inspecting the contactor and looking closely at the indoor evaporator coil.
These checks help find small problems before they turn into a complete loss of Cooling. Fast Affordable Air provides AC repair in Las Vegas and works on Heating and Cooling systems throughout Las Vegas, Henderson, North Las Vegas, and nearby areas of Clark County.
Checking the Temperature at the Air Vent
The first photo shows an infrared thermometer aimed at an air vent. The display reads approximately 67.7°F.
An infrared thermometer reads the surface temperature of the vent. It gives the technician a quick idea of whether the central Air Conditioner is producing cool air. It is useful, but it does not tell the whole story by itself.
A technician will often compare the supply-air temperature with the return-air temperature. Supply air is the cooled air coming into the room. Return air is the warmer air being pulled back into the HVAC system.
The difference between those two readings is called the temperature split. It works like subtracting two numbers in school. If the return air is 80°F and the supply air is 60°F, the temperature split is 20 degrees.
Only the 67.7°F vent reading is visible in these pictures, so a complete temperature split cannot be calculated from the photos alone. The reading still gives the technician an important starting point for the rest of the inspection.
Inspecting the AC Contactor
The second photo shows the system’s electrical contactor after it was removed for inspection. A contactor is a heavy-duty electrical switch. When the thermostat asks for Cooling, the contactor closes and sends power to major parts such as the compressor and outdoor fan motor.
Every time the air conditioning system turns on and off, the contactor opens and closes. After thousands of cycles, the metal contact points can become worn, burned, or pitted. Pitting means that the once-smooth metal surface has developed small rough spots or holes.
A worn contactor may cause the AC to start only sometimes. It can also make a buzzing or chattering noise. In more serious cases, it can become stuck and keep a component running when it should be off.
During the inspection, the technician checks the contact points, coil, wire terminals, and mounting area. The terminal screws also need to be tight. A loose electrical connection can create heat, much like a loose plug can become hot inside a wall outlet.
When replacement is needed, the new contactor must match the voltage and electrical rating required by the equipment manufacturer. Using the correct part helps the compressor and fan receive steady power without placing unnecessary stress on the system.
Examining the Indoor Evaporator Coil
Several photos show the evaporator coil inside the indoor section of the central Air Conditioning system. The coil contains many thin metal fins. These fins give heat a large surface where it can move from the indoor air into the cold refrigerant inside the coil.
In simple terms, the blower pushes warm household air across the cold coil. The coil removes heat from that air. The cooled air then travels through the ductwork and returns to the rooms.
Dust and buildup can be seen across portions of the coil fins. Even a thin layer can act like a blanket. It becomes harder for air to pass through the coil and harder for heat to move into the refrigerant.
During a coil inspection, the technician looks for dust, pet hair, bent fins, ice, water problems, corrosion, and oily areas. An oily area may sometimes point to a refrigerant leak, although proper leak-testing tools are needed before confirming one.
The coil must be cleaned carefully. The fins are thin and can bend easily. Harsh brushing or high water pressure may damage them. Depending on the amount and type of dirt, cleaning may involve a soft brush, a vacuum, compressed air used with care, or an approved coil cleaner.
Keeping this area open helps the blower move air more easily. It can improve indoor comfort, reduce long run times, and help the Heating and Cooling equipment use energy more effectively. Coil condition and airflow are normally checked during professional air conditioner maintenance .
Measuring the Electrical Load
The final pictures show a Fieldpiece SC440 True RMS meter. The display appears to show an electrical load of approximately 14.4 amps during testing.
An amp is a unit used to measure electrical current. Think of electricity like water moving through a pipe. Amperage tells the technician how much electrical current is flowing while the equipment is operating.
The 14.4-amp number should not be judged by itself. The technician must compare it with the rating printed on the AC equipment nameplate. The outdoor temperature, system stage, fan operation, and which wire was being measured can also change the reading.
A reading that is too high may point to an overloaded motor, weak electrical component, restricted airflow, high pressure, or a mechanical problem. A reading that is too low can also be important. It may show that a component is not operating under the expected load.
Using a professional HVAC meter lets the technician test the system instead of guessing. It also provides a number that can be recorded and compared during a future air conditioning tune-up .
System Checks After the Electrical Inspection
After inspecting the contactor, coil, and electrical load, the system can be restarted and watched through a complete Cooling cycle. The technician listens for unusual sounds and checks that the compressor, indoor blower, and outdoor fan start smoothly.
The technician can then take another supply-air reading, record the return-air temperature, inspect the air filter, and make sure water is draining away from the evaporator coil. These checks help confirm that the repair area is safe and that the central AC is moving cooled air through the home.
Recorded Project Details
- Supply-vent surface temperature shown in the photo was approximately 67.7°F
- The electrical contactor was removed for close inspection and service
- The evaporator-coil fins were inspected for dust, blockage, damage, and airflow problems
- A Fieldpiece SC440 was used for electrical testing
- The meter display showed approximately 14.4 amps during the captured test
- The amp reading requires comparison with the equipment nameplate before it can be evaluated
