MICHIGAN MECHANIC CORRECT FINALS ANSWERS
AND QUESTIONS SET A+
✔✔Symptoms of a failing condenser - ✔✔Symptoms of failure or restriction are a high
high-side discharge of pressures
✔✔Purpose of a evaporator - ✔✔Low pressure liquid changes into low pressure gas
✔✔Symptoms of a failing evaporator - ✔✔Symptoms of a failed component could be a
leak, sniffer test required
✔✔Purpose of a fixed orifice tube - ✔✔High pressure liquid enters, low pressure liquid
leaves
✔✔Symptoms of a clogged orifice tube - ✔✔Frost forming around the restricted area
✔✔Typical cause of a clogged orfice tube - ✔✔A clogged orifice tube is typically caused
by compressor failure
✔✔R-12 background - ✔✔R-12 is Freon and it destroys the ozone layer due process of
releasing CFCS into the air
✔✔What replaced R-12 - ✔✔R-134a
✔✔What replaced R134a - ✔✔R1234yf
✔✔What is operating pressure of low side pressure? - ✔✔Low pressure should be
between 20psi-40psi
✔✔What is operating pressure of high side pressure? - ✔✔High pressure should be
between 170psi-230psi
✔✔Effect of moisture in the system - ✔✔Moisture in the a/c system will turn to acid and
destroy all the components in the system
, ✔✔Effect of outside temperature & humidity on a system - ✔✔Temperature and
pressure are directly related. The higher the ambient temp, the higher your AC
pressures will be. Higher pressure's will lead to a higher outlet vent temperature.
Essentially, the air conditioning system does not work as well under extreme heat and
humid conditions
✔✔Symptoms of an overcharged system - ✔✔Both the low and high side pressures will
read higher than normal
✔✔How will the compressor act on an overcharged system - ✔✔The compressor will
run for a few seconds then turn off for long periods of time
✔✔Compressor clutch cycling operation - ✔✔If the pressure becomes too high, the
compressor clutch is cycled off, and if the pressure is too low, the compressor clutch is
cycled on.
✔✔Compressor clutch cycling testing - ✔✔power and ground should be sufficient and
the clutch should only have 3-5 ohms of resistance
✔✔How is compressor clutch cycling operated - ✔✔Cycling is accomplished through
the engaging and disengaging of an electromagnetic clutch which is actuated by a
module, relay and or switch
✔✔What are CFCs - ✔✔CFCs are a compound that destroys the ozone layer when
released into the air
✔✔What causes CFCs - ✔✔R12
✔✔Causes of both low side and high side pressures are low - ✔✔Undercharge or
restriction at either the orifice tube or expansion valve
✔✔Both low side and high side pressures are high - ✔✔Overcharge, faulty restriction
device or blockage of the high side
✔✔Low side pressure is low and high side pressure is high - ✔✔Restriction in a line or a
stuck closed expansion valve
✔✔Low side pressure is high and high side pressure is low - ✔✔An internally faulted
compressor or a stuck open expansion valve
✔✔Cooling system leak diagnosis - ✔✔Pressure test or dye test
AND QUESTIONS SET A+
✔✔Symptoms of a failing condenser - ✔✔Symptoms of failure or restriction are a high
high-side discharge of pressures
✔✔Purpose of a evaporator - ✔✔Low pressure liquid changes into low pressure gas
✔✔Symptoms of a failing evaporator - ✔✔Symptoms of a failed component could be a
leak, sniffer test required
✔✔Purpose of a fixed orifice tube - ✔✔High pressure liquid enters, low pressure liquid
leaves
✔✔Symptoms of a clogged orifice tube - ✔✔Frost forming around the restricted area
✔✔Typical cause of a clogged orfice tube - ✔✔A clogged orifice tube is typically caused
by compressor failure
✔✔R-12 background - ✔✔R-12 is Freon and it destroys the ozone layer due process of
releasing CFCS into the air
✔✔What replaced R-12 - ✔✔R-134a
✔✔What replaced R134a - ✔✔R1234yf
✔✔What is operating pressure of low side pressure? - ✔✔Low pressure should be
between 20psi-40psi
✔✔What is operating pressure of high side pressure? - ✔✔High pressure should be
between 170psi-230psi
✔✔Effect of moisture in the system - ✔✔Moisture in the a/c system will turn to acid and
destroy all the components in the system
, ✔✔Effect of outside temperature & humidity on a system - ✔✔Temperature and
pressure are directly related. The higher the ambient temp, the higher your AC
pressures will be. Higher pressure's will lead to a higher outlet vent temperature.
Essentially, the air conditioning system does not work as well under extreme heat and
humid conditions
✔✔Symptoms of an overcharged system - ✔✔Both the low and high side pressures will
read higher than normal
✔✔How will the compressor act on an overcharged system - ✔✔The compressor will
run for a few seconds then turn off for long periods of time
✔✔Compressor clutch cycling operation - ✔✔If the pressure becomes too high, the
compressor clutch is cycled off, and if the pressure is too low, the compressor clutch is
cycled on.
✔✔Compressor clutch cycling testing - ✔✔power and ground should be sufficient and
the clutch should only have 3-5 ohms of resistance
✔✔How is compressor clutch cycling operated - ✔✔Cycling is accomplished through
the engaging and disengaging of an electromagnetic clutch which is actuated by a
module, relay and or switch
✔✔What are CFCs - ✔✔CFCs are a compound that destroys the ozone layer when
released into the air
✔✔What causes CFCs - ✔✔R12
✔✔Causes of both low side and high side pressures are low - ✔✔Undercharge or
restriction at either the orifice tube or expansion valve
✔✔Both low side and high side pressures are high - ✔✔Overcharge, faulty restriction
device or blockage of the high side
✔✔Low side pressure is low and high side pressure is high - ✔✔Restriction in a line or a
stuck closed expansion valve
✔✔Low side pressure is high and high side pressure is low - ✔✔An internally faulted
compressor or a stuck open expansion valve
✔✔Cooling system leak diagnosis - ✔✔Pressure test or dye test
