310S Heating, Ventilation and Air Conditioning (HVAC) 2

Question 1

When diagnosing an A/C system with manifold gauges, what should be done FIRST to ensure accurate readings?

Accepted Answer

Run the engine and A/C system for 10 minutes to stabilize conditions

Answer

Recover all refrigerant from the system

Answer

Check the system for leaks using an electronic detector

Answer

Add refrigerant to bring pressures up to specification

Question 2

Both the high-side and low-side pressures are higher than normal specifications. This MOST likely indicates:

Accepted Answer

System overcharge or restricted condenser airflow

Answer

A faulty compressor with worn reed valves

Answer

Low refrigerant charge

Answer

A blocked expansion device

Question 3

Before opening an A/C system component for replacement, the technician MUST:

Accepted Answer

Recover the refrigerant using certified recovery equipment

Answer

Run the engine until refrigerant pressure drops to zero

Answer

Discharge refrigerant to atmosphere to relieve pressure safely

Answer

Flush the system with nitrogen to clear the refrigerant

Question 4

After replacing an A/C system component, what is the main purpose of evacuating the system with a vacuum pump?

Accepted Answer

To remove air and moisture from the system

Answer

To test the system for leaks before adding refrigerant

Answer

To circulate oil throughout the new component

Answer

To verify compressor operation before charging

Question 5

What vacuum level should be achieved when evacuating an A/C system to ensure adequate moisture removal?

Accepted Answer

500 microns (0.5 mm Hg) or lower

Answer

25 in Hg held for 5 minutes

Answer

Any vacuum that holds stable is acceptable

Answer

15 in Hg for a minimum of 30 minutes

Question 6

An A/C compressor clutch that rapidly cycles on and off during operation is MOST likely caused by:

Accepted Answer

Low refrigerant charge activating the low-pressure protection switch

Answer

An overcharged system activating the high-pressure cut-out switch

Answer

A faulty blower motor causing the evaporator to freeze over

Answer

Excessive compressor oil reducing system efficiency

Question 7

What type of oil must be used when servicing an R-134a automotive A/C system compressor?

Accepted Answer

PAG (Polyalkylene Glycol) oil

Answer

Mineral oil

Answer

Ester oil

Answer

ATF (Automatic Transmission Fluid)