Exam 10: System Controlsdiagnosis and Service of System Controls

What is the major disadvantage of the telltale light system?

Electronic control heads are being discussed.Technician A says all units have a connection to use a scan tool or diagnostic tool.Technician says the different brands use the same trouble code to indicate the same failure.Who is correct?

Technician A says a fuse can be replaced with one having a higher rating if the original size fuse keeps blowing.Technician B says it is always acceptable to replace a fuse with one having a lower rating.Who is correct?

The vacuum system is used to ____ the heater coolant valve and mode doors to achieve a desired preselected temperature and humidity level.

Any pressure below atmospheric pressure is considered a vacuum.

The sunload sensor monitors the temperature of the sunlight entering the vehicle.

Why is a diode used in the clutch coil circuit?

Which of the following is the best description of a pressure switch designated nc?

On an automatic temperature control system the blower motor circuit resistence is specified at 2.0 to 3.5 ohms.If the resistence in the circut falls to 1.5 ohms which of the following will be the most likely result?

Technician A says the pressure cycling switch directly opens and closes the electrical circuit to the compressor clutch coil.Technician B says the pressure cycling switch sends a signal to the microprocessor to turn the compressor on and off.Who is correct?

On a vehicle equipped with and automatic temperature control system the blower motor will not function when the vehicle is first started and heat is selected.Which of the following is the most likely cause?

A rattling noise is heard when the engine is running and the air conditioning is off.Technician A says this may be caused by a too narrow gap between the compressor's armature and rotor.Technician B says a quick accurate test is to switch on the air conditioning to see if the noise stops.Who is correct?

The connector for the blower speed control switch has melted.Which of the following is the most likely cause?

What could happen if the reservoir fails to hold vacuum.

Why do many systems use a check valve between the engine manifold supply vacuum hose and the reservoir tank?

Major circuits are protected by a fusible link or maxi-fuse.

The power control module sends a pulse width modulated signal to the blower motor to regulate blower speeds.

Name the components in the simplest type of heater/air conditioner control system.

The air conditioning compressor will not engage.When a scan tool is connected it indicates that there is no A/C request signal.Technician A says that the refrigerant system may have a faulty thermostatic expansion valve.Technician B says that an engine cooling system thermostat which is opening too soon could be the cause.Who is correct?

How does the thermostat control the in-vehicle temperature?