HVAC HVAC Troubleshooting Techniques

Question 1

What is the first step in systematic HVAC troubleshooting?

Accepted Answer

Gather information: verify the complaint, collect operational data, and identify symptoms

Answer

Replace the most likely failed component immediately

Answer

Check the refrigerant charge

Answer

Inspect the electrical panel for tripped breakers

Question 2

What does high discharge pressure and high suction pressure indicate in a refrigeration system?

Accepted Answer

Overcharge of refrigerant or non-condensables in the system

Answer

Low refrigerant charge

Answer

Dirty evaporator coil

Answer

Restricted metering device

Question 3

What does low suction pressure AND high suction superheat indicate?

Accepted Answer

Restricted or underfeeding metering device (TXV or orifice)

Answer

Overcharge of refrigerant

Answer

Non-condensables in the system

Answer

Condenser coil is dirty

Question 4

When using a clamp-on ammeter to diagnose an HVAC motor, what does a reading significantly above the nameplate FLA indicate?

Accepted Answer

The motor is mechanically or electrically overloaded

Answer

The motor is running efficiently at full capacity

Answer

The motor is running at partial load

Answer

The power factor is high, indicating good motor health

Question 5

What does a 'running amperage' that is LOW compared to nameplate FLA typically indicate for a compressor?

Accepted Answer

The compressor has low refrigerant charge, worn valves, or is not fully loaded

Answer

The compressor is working efficiently

Answer

The capacitor is overcharged

Answer

The power supply voltage is too high

Question 6

How do you check for a leaking compressor valve using manifold gauges?

Accepted Answer

With the system off, observe if suction and discharge pressures equalize quickly (within minutes) through the compressor

Answer

Shut off the system, equalize pressures, and measure how quickly pressures equalize overnight

Answer

Measure the pressure difference between liquid and suction lines during operation

Answer

Check the discharge temperature at the compressor outlet

Question 7

What is the 'touch test' for diagnosing electrical components, and what are its limitations?

Accepted Answer

Feeling for unusual heat in components — useful for identifying overheating but not precise; requires confirmation with instruments

Answer

Touching components to feel for vibration — reliable for all diagnostics

Answer

Touching wires to check for voltage — never appropriate

Answer

Feeling for moisture on refrigerant lines — precise moisture detection method

Question 8

What does a 'megohmmeter' (megger) test on a motor winding check for?

Accepted Answer

Insulation breakdown (current leakage from winding to motor frame/ground)

Answer

Winding resistance in ohms for continuity

Answer

Capacitor microfarad rating

Answer

Motor starting torque

Question 9

What does 'static pressure test' of an air distribution system reveal?

Accepted Answer

Airflow restrictions in ducts, filters, and coils that may be causing comfort problems or equipment strain

Answer

The refrigerant pressure in the system

Answer

The static charge buildup in ductwork

Answer

The moisture level in the ductwork

Question 10

When troubleshooting a system that short-cycles, what are the most common causes?

Accepted Answer

Oversized equipment, low refrigerant charge causing low-pressure lockout, dirty filters, or thermostat problems

Answer

Low refrigerant charge only

Answer

Defective condenser fan motor only

Answer

High outdoor ambient temperature only