CFC Automotive Air Conditioning Service 4 — Questions and Answers
Question 1: What does a sight glass in an automotive A/C system that shows bubbles while the compressor is running typically indicate?
- Normal operation at high load
- Low refrigerant charge (Correct answer)
- Refrigerant overcharge
- Water contamination
Correct answer: Low refrigerant charge
Bubbles in the sight glass indicate incomplete liquid flow to the expansion valve, most commonly caused by low refrigerant charge.
Question 2: R-134a must NOT be mixed with R-12 because:
- They have different boiling points causing inefficiency
- They are incompatible — different oils are used and mixing creates unsafe pressures and deposits (Correct answer)
- R-12 is cheaper and dilutes the charge
- R-134a condenses at a higher temperature
Correct 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.
Question 3: When transferring refrigerant from a recovery cylinder to a charging cylinder, the technician should:
- Heat both cylinders with an open flame to speed transfer
- Never transfer refrigerant between cylinders — use dedicated equipment
- Weigh the refrigerant and transfer at room temperature using appropriate hoses (Correct answer)
- Vent excess vapor before transferring
Correct 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.
Question 4: An automotive technician discovers an A/C system contains R-12. To legally service this system they must:
- Add R-134a as a drop-in replacement
- Use only Section 609-certified equipment and a technician certified for CFC refrigerants (Correct answer)
- Vent the small amount of R-12 and recharge with R-134a
- Send the vehicle to a dealer — independent shops cannot service R-12 systems
Correct 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.
Question 5: 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:
- Low refrigerant charge
- Clogged orifice tube
- Compressor internal failure (not pumping) (Correct answer)
- Faulty expansion valve stuck open
Correct 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.
Question 6: Which of the following is a legal method of disposing of a vehicle with an intact, charged A/C system?
- Crush it immediately — the compressor will seal the refrigerant
- Recover the refrigerant with certified equipment before crushing or recycling (Correct answer)
- Remove the compressor and discard it with the refrigerant inside
- Drain the refrigerant oil so the system pressure drops below hazardous levels
Correct 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.
Question 7: What is the maximum allowable leak rate for automotive A/C systems before a technician is required to repair the leak under EPA rules?
- There is no specific leak rate limit for MVAC systems; any knowingly venting is prohibited (Correct answer)
- 0.5 oz/year
- 2 lbs/year
- 10% of system charge per year
Correct 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.
CFC Automotive Air Conditioning Service 4
What does a sight glass in an automotive A/C system that shows bubbles while the compressor is running typically indicate?