Automotive Air Conditioning Service Flashcards

What does a sight glass in an automotive A/C system that shows bubbles while the compressor is running typically indicate?

Answer: Low refrigerant charge

Bubbles in the sight glass indicate incomplete liquid flow to the expansion valve, most commonly caused by low refrigerant charge.

R-134a must NOT be mixed with R-12 because:

Answer: They are incompatible — different oils are used and mixing creates unsafe pressures and deposits

R-134a uses PAG oil while R-12 uses mineral oil; mixing refrigerants causes chemical incompatibility, pressure irregularities, and can damage system components.

When transferring refrigerant from a recovery cylinder to a charging cylinder, the technician should:

Answer: Weigh the refrigerant and transfer at room temperature using appropriate hoses

Refrigerant transfer between cylinders must be done gravimetrically (by weight) using proper hoses at ambient temperature — open flames near refrigerant cylinders are dangerous.

An automotive technician discovers an A/C system contains R-12. To legally service this system they must:

Answer: Use only Section 609-certified equipment and a technician certified for CFC refrigerants

R-12 is a Class I ODS refrigerant; servicing requires Section 609-certified technicians using approved recovery equipment rated for CFCs.

The compressor clutch engages but the A/C system produces no cooling. Low-side pressure is very high and high-side pressure is near low-side pressure. This indicates:

Answer: Compressor internal failure (not pumping)

Equal pressures on both sides with the compressor engaged indicate the compressor is spinning but not pumping — an internal mechanical failure.

Which of the following is a legal method of disposing of a vehicle with an intact, charged A/C system?

Answer: Recover the refrigerant with certified equipment before crushing or recycling

All refrigerant must be recovered using EPA-certified equipment before a vehicle is crushed, scrapped, or otherwise disposed of.

What is the maximum allowable leak rate for automotive A/C systems before a technician is required to repair the leak under EPA rules?

Answer: There is no specific leak rate limit for MVAC systems; any knowingly venting is prohibited

Unlike stationary refrigeration, MVAC regulations prohibit knowingly venting refrigerant but do not set a specific annual leak rate threshold — technicians must repair leaks found during service.