CSLB General Building (B) — All Questions
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In an automotive A/C system, the compressor's job is to:
- a.Condense refrigerant into a liquid
- b.Store refrigerant
- c.Raise refrigerant pressure and circulate it through the system✓
- d.Absorb moisture from the refrigerant
The compressor pressurizes low-pressure refrigerant vapor and pumps it through the system, raising its temperature and pressure before the condenser. It is the pump that drives the refrigeration cycle. A failed compressor clutch or internal damage stops cooling.
The component that changes high-pressure refrigerant vapor into a liquid by removing heat is the:
- a.Condenser✓
- b.Evaporator
- c.Accumulator
- d.Expansion valve
The condenser, mounted in front of the radiator, rejects heat so the high-pressure vapor condenses into a liquid. Airflow across it is essential; a blocked or dirty condenser causes high pressures and poor cooling. The evaporator, by contrast, absorbs heat inside the vehicle.
The evaporator in the passenger compartment:
- a.Compresses the refrigerant
- b.Rejects heat to the outside air
- c.Stores excess refrigerant
- d.Absorbs heat from cabin air, cooling it✓
As low-pressure liquid refrigerant boils in the evaporator, it absorbs heat from the cabin air blown across it, cooling and dehumidifying the air. A restricted or iced evaporator reduces airflow and cooling. Proper refrigerant charge and airflow keep it working correctly.
Technician A says overcharging an A/C system improves cooling. Technician B says overcharging raises system pressures and can reduce cooling and damage the compressor. Who is correct?
- a.Technician A only
- b.Technician B only✓
- c.Both A and B
- d.Neither A nor B
Overcharging raises high-side pressure, reduces cooling efficiency, and can damage the compressor with liquid slugging. The correct charge, measured by weight, is critical. Technician A is wrong; more refrigerant is not better.
The expansion valve or orifice tube controls:
- a.Compressor speed
- b.Blower motor voltage
- c.The flow of refrigerant into the evaporator, causing a pressure drop✓
- d.Cabin air recirculation
The metering device drops the refrigerant pressure and controls flow into the evaporator, allowing it to boil and absorb heat. A restricted orifice or stuck valve causes poor cooling and abnormal pressures. It separates the high side from the low side of the system.
The desiccant in a receiver-drier or accumulator is used to:
- a.Absorb moisture from the refrigerant✓
- b.Add oil to the system
- c.Increase refrigerant pressure
- d.Cool the condenser
The desiccant removes moisture that would otherwise form acids and ice, protecting the system. It should be replaced whenever the system is opened for major service. Saturated desiccant can break down and contaminate the system.
Technician A says a low refrigerant charge typically shows low readings on both gauges with poor cooling. Technician B says the leak should be repaired before recharging to the correct weight. Who is correct?
- a.Technician A only
- b.Technician B only
- c.Both A and B✓
- d.Neither A nor B
An undercharge shows low readings on both gauges with weak cooling and rapid cycling, and any leak must be repaired before recharging by weight. Both technicians are correct. Dye or an electronic detector locates the leak source.
Technician A says cabin heat comes from engine coolant flowing through the heater core. Technician B says a leaking heater core can fog the windshield and leave a sweet smell. Who is correct?
- a.Both A and B✓
- b.Technician A only
- c.Technician B only
- d.Neither A nor B
The heater core transfers heat from hot engine coolant to cabin air, and a leaking core lets coolant fog the glass and produce a sweet odor. Both technicians are correct. A clogged core or low coolant reduces heat output.
Technician A says a stuck-closed blend-air door can cause no heat even with a good heater core. Technician B says a failed blower motor can cause no airflow from the vents. Who is correct?
- a.Technician A only
- b.Technician B only
- c.Both A and B✓
- d.Neither A nor B
A blend door controls how much air passes over the heater core, so a stuck door can cause no heat, and a failed blower stops airflow entirely. Both technicians are correct. Actuator and door faults are common causes of temperature-control complaints.
Before servicing an A/C system, refrigerant must be:
- a.Recovered with approved equipment, not vented to the atmosphere✓
- b.Vented outdoors quickly
- c.Mixed with fresh oil
- d.Frozen in the condenser
Regulations require recovering refrigerant with certified equipment rather than releasing it, because it is a controlled substance. Recovery, recycling, and recharging equipment protects the environment and allows accurate recharging. Technicians handling refrigerant must be certified.
An A/C compressor clutch that will not engage could be caused by all of the following EXCEPT:
- a.A low-refrigerant lockout from the pressure switch
- b.A blown clutch fuse or relay
- c.An open clutch coil
- d.A clogged cabin air filter✓
The clutch may fail to engage due to a low-charge lockout, electrical faults, or an open coil, but a dirty cabin filter only reduces airflow, not clutch engagement. Diagnosis checks power, ground, and the pressure switches. A cabin filter affects volume, not the refrigerant cycle.
Higher-than-normal readings on both the high and low sides of an A/C system, with poor cooling, could indicate:
- a.A low refrigerant charge
- b.An overcharge or a condenser airflow/cooling problem✓
- c.An open blower resistor
- d.A stuck-open thermostat
High readings on both gauges often point to an overcharge or inadequate condenser cooling from a blocked condenser or inoperative cooling fan. Verifying charge weight and fan operation is the next step. Correcting airflow and charge restores normal pressures.