CRST Troubleshooting & Repair Techniques 3

Question 1

A TXV-equipped system has low suction pressure and low superheat simultaneously. What is the MOST likely cause?

Accepted Answer

TXV stuck closed

Answer

A TXV stuck in the closed position starves the evaporator, causing low suction pressure; low superheat indicates little refrigerant is vaporizing past the valve.

Question 2

What does a bubbling or foamy sight glass indicate in a refrigeration system?

Accepted Answer

Low refrigerant or liquid line restriction

Answer

Bubbles in the sight glass indicate the liquid refrigerant is flashing to vapor, which points to a low charge or restriction upstream.

Question 3

A compressor that hums but fails to start most likely has a faulty:

Accepted Answer

Start capacitor or start relay

Answer

A failed start capacitor or start relay prevents the start winding from providing enough torque to overcome compressor inertia during startup.

Question 4

Frost forming on the suction line all the way back to the compressor indicates:

Accepted Answer

Low superheat and possible liquid floodback

Answer

Suction line frost extending to the compressor indicates liquid refrigerant is returning, which can cause liquid slugging and compressor damage.

Question 5

When recovering refrigerant from a system with a hermetic compressor burnout, the technician should:

Accepted Answer

Use a dedicated recovery cylinder and filter to avoid cross-contamination

Answer

Burnout contaminates refrigerant with acids and carbon; it must be recovered into a dedicated cylinder and sent for reclamation or disposal.

(CRST) Certified Refrigeration Service Technician Practice Test

(CRST) Certified Refrigeration Service Technician Practice Test

CRST Troubleshooting & Repair Techniques 3