Air Conditioning Repair Car Air Conditioning Repair 5

Question 1

What does a bubbling or foamy sight glass indicate in a vehicle AC system that uses one?

Accepted Answer

Low refrigerant charge

Answer

Bubbles or foam in the sight glass indicate that refrigerant is flashing to vapor in the liquid line due to insufficient charge, which reduces system efficiency.

Question 2

Which refrigerant is now required in new passenger vehicles sold in the US due to its lower global warming potential?

Accepted Answer

R-1234yf

Answer

R-1234yf has a global warming potential (GWP) of less than 1 compared to R-134a's GWP of 1,430, making it the mandated refrigerant for new US passenger cars.

Question 3

A technician measures superheat at the evaporator outlet and finds it excessively high. What does this indicate about the TXV?

Accepted Answer

TXV is stuck closed or restricted, starving the evaporator

Answer

High superheat means refrigerant is fully evaporated well before the evaporator outlet, indicating insufficient refrigerant flow from a restricted or malfunctioning TXV.

Question 4

What is the primary reason an AC system should never be charged by weight alone without also checking operating pressures?

Accepted Answer

System restrictions or component failures won't show in weight but will affect pressures

Answer

Charging by weight adds the correct amount of refrigerant but cannot detect restrictions, valve failures, or other issues that manifest only in abnormal pressure readings.

Question 5

When diagnosing an AC system, a technician finds both high-side and low-side pressures are too high. What is the most likely cause?

Accepted Answer

Expansion device stuck open or overcharged system

Answer

Uniformly elevated pressures on both sides indicate either an overcharge or an expansion device stuck open that allows too much refrigerant to flood the low side.

Air Conditioning Repair Practice Test

Air Conditioning Repair Practice Test

Air Conditioning Repair Car Air Conditioning Repair 5