Michigan Mechanic Certification- HVAC
Cooling system leak diagnosis - ANSPressure test or dye test
Purpose of a radiator - ANSThe purpose of the radiator is to dissipate heat that is picked up
by coolant in the engine into the air passing through its fins and tubes
Symptoms of low coolant - ANSEngine overheating and no heat from the HVAC system
Purpose of the thermostat - ANSThe purpose of the thermostat is to trap the coolant in the
engine until it reaches it operating temperature
Cause of low heater output - ANSLow coolant level, clogged heater core, leaking heater core
Heater core hose routing - ANSThe supply hose from the heater core should run from the
closed side of the thermostat to the heater core and the return hose should run from the
heater core to the engine
Heater core operation - ANSThe blower motor blows air through the heater core fins and is
warmed through the principle of conduction
Heater control valve purpose - ANSThis valve controls the flow of the coolant to the heater
core to control the temperature of the air desired by the operator
Radiator cap testing - ANSTo test pressure test it using an adapter and a coolant pressure
tester and the value marked on the pressure cap
Reciever drier purpose - ANSMay contain a filter or strainer to catch and trap foreign
particles and dirt
Reciever drier location - ANSLocated on the high side of the system between the condenser
and the evaporator
Ambient temperature switch purpose - ANSMonitors temperature by increasing or
decreasing with resistance as temperature changes
Symptoms of a failing ambient temperature switch - ANSA bad temperature switch could
cause an inoperative clutch or input problems
Orifice expansion tube operation - ANSHas a valve that can vary the size of the opening to
allow more or less liquid refrigerant through to the evaporator
Orifice expansion tube purpose - ANSHigh pressure liquid enters, low pressure liquid leaves
Purpose of a compressor - ANSLow pressure gas enters and high pressure gas leaves
Cooling system leak diagnosis - ANSPressure test or dye test
Purpose of a radiator - ANSThe purpose of the radiator is to dissipate heat that is picked up
by coolant in the engine into the air passing through its fins and tubes
Symptoms of low coolant - ANSEngine overheating and no heat from the HVAC system
Purpose of the thermostat - ANSThe purpose of the thermostat is to trap the coolant in the
engine until it reaches it operating temperature
Cause of low heater output - ANSLow coolant level, clogged heater core, leaking heater core
Heater core hose routing - ANSThe supply hose from the heater core should run from the
closed side of the thermostat to the heater core and the return hose should run from the
heater core to the engine
Heater core operation - ANSThe blower motor blows air through the heater core fins and is
warmed through the principle of conduction
Heater control valve purpose - ANSThis valve controls the flow of the coolant to the heater
core to control the temperature of the air desired by the operator
Radiator cap testing - ANSTo test pressure test it using an adapter and a coolant pressure
tester and the value marked on the pressure cap
Reciever drier purpose - ANSMay contain a filter or strainer to catch and trap foreign
particles and dirt
Reciever drier location - ANSLocated on the high side of the system between the condenser
and the evaporator
Ambient temperature switch purpose - ANSMonitors temperature by increasing or
decreasing with resistance as temperature changes
Symptoms of a failing ambient temperature switch - ANSA bad temperature switch could
cause an inoperative clutch or input problems
Orifice expansion tube operation - ANSHas a valve that can vary the size of the opening to
allow more or less liquid refrigerant through to the evaporator
Orifice expansion tube purpose - ANSHigh pressure liquid enters, low pressure liquid leaves
Purpose of a compressor - ANSLow pressure gas enters and high pressure gas leaves
