Heating and Air Conditioning Flashcards

Under the Clean Air Act, what is required for a technician to service motor vehicle A/C systems for pay?

Answer: EPA Section 609 certification

Section 609 certification is required to service MVAC systems and buy small cans of refrigerant for professional use.

What safety characteristic of R-1234yf requires special service equipment and procedures?

Answer: It is mildly flammable (A2L classification)

R-1234yf is classified A2L, mildly flammable, so equipment meeting SAE J2843 and unique fittings are required.

On a hybrid vehicle with a high-voltage electric A/C compressor, why must the correct specified oil (often POE) be used?

Answer: Wrong oil can reduce electrical insulation and create a shock or failure risk

The oil contacts the motor windings, so conductive or incorrect oil can compromise high-voltage insulation.

Why is a deep vacuum pulled on an A/C system after it has been opened for repair?

Answer: To remove air and boil off moisture at low pressure

Lowering pressure lowers water's boiling point so moisture vaporizes and is removed along with air.

Which component should typically be replaced whenever an A/C system is opened for major repair or has been left open to the atmosphere?

Answer: Receiver-drier or accumulator

The desiccant in the drier or accumulator saturates with moisture and must be replaced to protect the system.

On a TXV-type A/C system, where is the receiver-drier located?

Answer: High side between the condenser and expansion valve

The receiver-drier stores liquid refrigerant on the high side ahead of the expansion valve.

A customer complains of a musty odor when the A/C is first turned on. What is the most appropriate repair?

Answer: Clean the evaporator with an approved treatment and replace the cabin air filter

Mold and bacteria on the damp evaporator cause the odor and are treated with evaporator cleaner and a fresh filter.