Cooling system leak diagnosis - ANSWER Pressure test or dye test
Purpose of a radiator - ANSWER The 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 - ANSWER Engine overheating and no heat from the HVAC sys-
tem
Purpose of the thermostat - ANSWER The purpose of the thermostat is to trap the cool-
ant in the engine until it reaches it operating temperature
Cause of low heater output - ANSWER Low coolant level, clogged heater core, leaking
heater core
Heater core hose routing - ANSWER The 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 - ANSWER The blower motor blows air through the heater core
fins and is warmed through the principle of conduction
Heater control valve purpose - ANSWER This 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 - ANSWER To test pressure test it using an adapter and a coolant
pressure tester and the value marked on the pressure cap
1
, Reciever drier purpose - ANSWER May contain a filter or strainer to catch and trap for-
eign particles and dirt
Reciever drier location - ANSWER Located on the high side of the system between the
condenser and the evaporator
Ambient temperature switch purpose - ANSWER Monitors temperature by increasing or
decreasing with resistance as temperature changes
Symptoms of a failing ambient temperature switch - ANSWER A bad temperature switch
could cause an inoperative clutch or input problems
Orifice expansion tube operation - ANSWER Has 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 - ANSWER High pressure liquid enters, low pressure liq-
uid leaves
Purpose of a compressor - ANSWER Low pressure gas enters and high pressure gas leaves
Symptoms of a failing compressor - ANSWER Pressures are going to be equal
Purpose of a condenser - ANSWER Low pressure gas enters and high pressure gas leaves
Symptoms of a failing condenser - ANSWER Symptoms of failure or restriction are a high
high-side discharge of pressures
Purpose of a evaporator - ANSWER Low pressure liquid changes into low pressure gas
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Purpose of a radiator - ANSWER The 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 - ANSWER Engine overheating and no heat from the HVAC sys-
tem
Purpose of the thermostat - ANSWER The purpose of the thermostat is to trap the cool-
ant in the engine until it reaches it operating temperature
Cause of low heater output - ANSWER Low coolant level, clogged heater core, leaking
heater core
Heater core hose routing - ANSWER The 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 - ANSWER The blower motor blows air through the heater core
fins and is warmed through the principle of conduction
Heater control valve purpose - ANSWER This 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 - ANSWER To test pressure test it using an adapter and a coolant
pressure tester and the value marked on the pressure cap
1
, Reciever drier purpose - ANSWER May contain a filter or strainer to catch and trap for-
eign particles and dirt
Reciever drier location - ANSWER Located on the high side of the system between the
condenser and the evaporator
Ambient temperature switch purpose - ANSWER Monitors temperature by increasing or
decreasing with resistance as temperature changes
Symptoms of a failing ambient temperature switch - ANSWER A bad temperature switch
could cause an inoperative clutch or input problems
Orifice expansion tube operation - ANSWER Has 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 - ANSWER High pressure liquid enters, low pressure liq-
uid leaves
Purpose of a compressor - ANSWER Low pressure gas enters and high pressure gas leaves
Symptoms of a failing compressor - ANSWER Pressures are going to be equal
Purpose of a condenser - ANSWER Low pressure gas enters and high pressure gas leaves
Symptoms of a failing condenser - ANSWER Symptoms of failure or restriction are a high
high-side discharge of pressures
Purpose of a evaporator - ANSWER Low pressure liquid changes into low pressure gas
2
