EPA 609 Practice Test 3 Flashcards

R-134a MVAC systems typically operate with what high-side pressure range at normal ambient temperatures (approximately 90°F)?

Answer: 180-250 psig

R-134a automotive A/C systems typically operate with high-side pressures of approximately 180-250 psig at 90°F ambient temperature with the engine running and A/C at full cooling. Pressures vary with ambient temperature, compressor speed, and load. High-side pressures significantly outside this range indicate system problems such as overcharge, condenser airflow obstruction, or refrigerant contamination.

What is the purpose of the condenser in an automotive A/C system and where is it located?

Answer: Rejects heat from refrigerant to ambient air, condensing refrigerant to liquid; located in front of the radiator

The condenser in an MVAC system is located in front of the radiator (or parallel to it) in the engine compartment where it receives maximum airflow. It rejects the heat absorbed by the refrigerant from the cabin and compressor work, condensing the high-pressure refrigerant vapor into a high-pressure liquid. Condenser airflow is critical — blockage by leaves or debris causes high-side pressure rise and poor cooling.

Under EPA Section 609, what type of equipment must automotive service shops use to service MVAC refrigerant systems?

Answer: EPA-approved refrigerant recover/recycle/recharge (RRR) equipment specifically designed for MVAC service

Section 609 requires the use of EPA-approved refrigerant recovery/recycling/recharge (RRR) equipment specifically designed for MVAC service. This equipment must meet SAE standards (J2788 for R-134a, J2843 for R-1234yf) for recovery efficiency, oil separation, moisture removal, and recharge accuracy. Standard Section 608 recovery equipment designed for stationary systems is not approved for MVAC use under Section 609.

What causes an intermittent cooling problem in an automotive A/C system that cools normally at first but gradually loses effectiveness as the car warms up?

Answer: Expansion valve or orifice tube icing due to moisture in the system

Moisture in an MVAC system can cause intermittent cooling loss by freezing at the expansion device (orifice tube or TXV). Initially, the system cools normally. As refrigerant flow continues, moisture concentrates at the restriction point and freezes, blocking refrigerant flow and causing the evaporator to warm up. As the system sits, the ice melts and cooling resumes — a tell-tale sign of moisture contamination requiring drier replacement.

R-1234yf service requires dedicated equipment that cannot be used interchangeably with R-134a equipment. Why?

Answer: R-1234yf's mild flammability and distinct properties require dedicated fittings and purging procedures to prevent mixing and ignition risk

R-1234yf is classified A2L (mildly flammable), unlike R-134a (A1, non-flammable). SAE standards mandate dedicated, non-interchangeable service equipment for R-1234yf with unique fittings (to prevent accidental cross-connection), internal purging to prevent mixing with residual R-134a in hoses, and special precautions for handling its mild flammability. Mixing the two refrigerants also degrades performance.

When recharging an MVAC system to the manufacturer's specified weight, which method provides the most accurate charge?

Answer: Using the vehicle manufacturer's weight specification with a calibrated charging scale

The most accurate MVAC recharge method is to weigh the refrigerant being added using a calibrated charging scale, targeting the vehicle manufacturer's specified charge weight (typically found on the underhood A/C label). Pressure-based and sight glass-based methods are less precise and do not account for system variations. Modern R-134a and R-1234yf RRR equipment has integrated scales for precise charging.