HVAC Troubleshooting 2

Question 1

A heat pump is running in heating mode but the discharge air feels cool. What is the most likely cause?

Accepted Answer

Reversing valve stuck in cooling position

Answer

A reversing valve stuck in the cooling position causes the heat pump to pump heat outdoors instead of indoors, resulting in cool discharge air during heating mode.

Question 2

An air conditioner short-cycles (turns on and off frequently). Which of the following is the LEAST likely cause?

Accepted Answer

Dirty evaporator coil

Answer

A dirty evaporator coil typically causes the unit to run longer or freeze up, not short-cycle; oversized equipment, low charge, and faulty contactors are common short-cycling causes.

Question 3

A technician measures suction pressure of 55 psig and discharge pressure of 175 psig on an R-22 system. What condition does this indicate?

Accepted Answer

Low refrigerant charge

Answer

Low suction and low discharge pressures on an R-22 system indicate a refrigerant undercharge, reducing the system's capacity.

Question 4

A gas furnace ignites but the burner shuts off after a few seconds. What component is most likely faulty?

Accepted Answer

Flame sensor (flame rod)

Answer

A dirty or failed flame sensor cannot verify the presence of a flame, causing the control board to shut off gas flow as a safety measure.

Question 5

A condensate drain line is clogged on a high-efficiency furnace. What symptom would you expect?

Accepted Answer

Unit shuts down on pressure switch lockout

Answer

A clogged condensate drain causes water to back up and block the pressure switch port, causing the furnace to lockout on a pressure switch fault.

HVAC Practice Test

HVAC Practice Test

HVAC Troubleshooting 2