GM GM HVAC and Climate Control 1 — Questions and Answers
Question 1: What refrigerant is used in most modern GM vehicle HVAC systems produced after 2021?
- R-134a
- R-1234yf (Correct answer)
- R-22
- R-410a
Correct answer: R-1234yf
GM transitioned to R-1234yf refrigerant in newer models due to its significantly lower global warming potential compared to R-134a.
Question 2: Before opening a GM AC system for service, a technician must first perform which step?
- Add fresh refrigerant to top off the system
- Recover all refrigerant using a certified recovery machine (Correct answer)
- Flush the condenser with water
- Replace the receiver-drier before any other step
Correct answer: Recover all refrigerant using a certified recovery machine
EPA regulations require all refrigerant to be recovered with certified recovery equipment before opening any part of the AC system to prevent atmospheric release.
Question 3: What component in a GM HVAC system is responsible for removing moisture from the refrigerant circuit?
- Expansion valve
- Condenser
- Receiver-drier or accumulator (Correct answer)
- Evaporator core
Correct answer: Receiver-drier or accumulator
The receiver-drier (on TXV systems) or accumulator (on orifice tube systems) contains desiccant material that absorbs moisture from the refrigerant to prevent system damage.
Question 4: On a GM dual-zone climate control system, what allows each side of the vehicle to maintain independent temperature settings?
- Two separate compressors
- A single blower with dual evaporators
- A blend door actuator for each temperature zone (Correct answer)
- Two separate refrigerant circuits
Correct answer: A blend door actuator for each temperature zone
Dual-zone climate systems use separate blend door actuators for the driver and passenger sides, independently controlling air mixing to achieve different temperatures.
Question 5: A customer complains their GM vehicle's AC blows cold then warm intermittently. Which component is the most likely cause?
- Faulty blend door actuator
- Icing of the evaporator core due to a low refrigerant charge (Correct answer)
- Failed condenser fan
- Cracked heater core
Correct answer: Icing of the evaporator core due to a low refrigerant charge
A low refrigerant charge causes the evaporator to drop below freezing, forming ice that temporarily blocks airflow; as the ice melts cooling resumes, creating an intermittent symptom.
Question 6: What is the purpose of the orifice tube in a GM AC system that uses this design?
- Compress refrigerant vapor before entering the condenser
- Meter refrigerant flow into the evaporator by reducing pressure (Correct answer)
- Store excess refrigerant during low-demand operation
- Sense evaporator outlet temperature for compressor control
Correct answer: Meter refrigerant flow into the evaporator by reducing pressure
The orifice tube is a fixed restriction that meters refrigerant flow into the evaporator, causing a pressure drop that allows the refrigerant to absorb heat and cool the cabin.
GM GM HVAC and Climate Control 1
What refrigerant is used in most modern GM vehicle HVAC systems produced after 2021?