Automotive HVAC 1 Quiz 2

What are the three airflow sections in a typical HVAC system?

- Air inlet section - Plenum section - Air distribution section

Ethylene glycol antifreeze contains:

- Anticorrosion additives - Rust inhibitors - Water pump lubricants

What steps are included in performing a visual inspection of the heating system?

- Coolant level and condition - Water pump drive belt condition and proper tension - Radiator or condenser for possible clogged or restricted areas - Temperature of the heater hoses - Proper airflow across the heater core

Coolant flows through the engine in one of the following ways:

- Parallel flow system - Series flow system - Series-parallel flow system

Coolant testing

- Visual inspection - Freeze/boiling point - pH - Coolant voltage

What are 10 common causes of overheating?

1) Low coolant level 2) Clogged radiator 3) Defective cooling fan 4) Incorrect ignition timing 5) Defective coolant pump belt 6) Defective pressure cap 7) Defective coolant pump 8) Defective thermostat 9) Frozen coolant 10) Engine problem

What is included in a complete electrical circuit?

1) Power source 2) Protection from harmful overloads 3) The power path for the current to flow through, from the power source to the resistance. 4) The electrical load or resistance. 5) A return path (or ground) for the electrical current from the load back to the power source so that there is a complete circuit. 6) Switches and controls that turn the circuit on and off.

The heating element is designed to warm the seat and/or back of the seat to about __.

100 degrees Fahrenheit

Most experts recommend that the system be drawn to how many microns?

500 or lower.

When testing a relay using an ohmmeter, which two terminals should be touched to measure the coil resistance?

86 and 85

Why is a 50/50 mixture of antifreeze and water commonly used as coolant?

A 50/50 mixture provides the best combination of freezing protection and heat transfer ability of the coolant.

Why is a cooling system pressurized?

A cooling system is pressurized to prevent boiling until above the normal boiling point of the coolant and to help prevent cavitation (bubbles or foaming) inside the coolant pump.

The upper radiator hose collapses when the engine cools. What is the most likely cause?

A defective pressure cap.

Explain the operation of a thermostatic cooling fan.

A thermostatic cooling fan senses air temperature and through a silicone coupling fan drive engages the engine-driven cooling fan only when needed.

Some cabin filters contain __ to absorb odors.

Activated charcoal

A container of R-134a tested at a pressure of 115 psi at an ambient temperature of 75 degrees Celsius.

Air is in the refrigerant.

What types of coolant are used in vehicles?

All factory installed coolant is ethylene-glycol based and currently includes: - OAT, HOAT, and PHOAT formulations.

What are ampere, volt, and ohm?

Ampere - Current flow Volt - Electrical flow Ohm - Resistance to the flow of current through a conductor

Rear air conditioning systems use __.

An orifice tube to control the refrigerant flow into the evaporator and a TXV with the rear evaporator.

Water pumps __.

Are driven by the engine crankshaft or camshaft.

The coolant heat storage system is being discussed. Technician A says that the water valve is driven by an electric motor. Technician B says that the storage tank has its own electric water pump.

Both Technician A and B.

Technician A says that a good relay should measure between 60 and 100 ohms across the coil terminals. Technician B says that OL should be displayed on an ohmmeter when touching terminals 30 and 87.

Both Technicians A and B.

Technician A says that some cabin filters are accessible behind the glove compartment. Technician B says that some cabin filters are accessible from under the hood.

Both Technicians A and B.

Two technicians are discussing testing coolant for proper pH. Technician A says that coolant has a pH above 7 when new and becomes lower with use in an engine. Technician B says that OAT and PHOAT coolants have lower pH when new compared to the old green IAT coolant.

Both Technicians A and B.

What type of pump is a typical water pump?

Centrifugal

What is commonly wrong when the heat from a heater "comes and goes?"

Cooling system is low on coolant.

Describe how to perform a drain, flush, and refill procedure performed on a cooling system.

Cooling system service involves draining the system and forcing water (sometimes with chemical cleaners) through the system and refilling the system with a 50/50 solution of antifreeze and water. Care should be exercised to be assured that all air is burped from the system.

PHOAT coolant is what color?

Dark green

High resistance in an electrical circuit can cause __.

Dim lights, slow motor operation, and clicking of relays or solenoids.

Why is an HEV motor/electronics system separate from that of the ICE?

Electric motors and the motor controls tend to operate more efficiently at lower temperatures. The engine cooling system runs too hot to allow these components to operate at peak efficiency, so a separate low-temperature system is often used.

Adding a chemical to make ethylene glycol coolant bitter to the taste is called __.

Embittered

Coolant is water and __.

Ethylene glycol

DEX-COOL is __.

Ethylene glycol and is silicate and phosphate free.

Semiconductors

Exactly four electrons in their atom's outer orbit.

Why is a feedback potentiometer used on an electric actuator?

Feedback potentiometers are used to provide the controller with the actual position of the door or valve.

What is the difference between galvanic activity and electrolysis?

Galvanic activity is voltage production without an outside source of voltage, whereas electrolysis is created when the vehicle has a poor ground connection.

Asian red coolant is what type?

HOAT

A typical vehicle heater works by __.

Heat transfers from the coolant, to the fins, and to the air passing through the core.

How does the coolant heat storage work?

Heated coolant is stored during normal vehicle operation and is then used to warm the engine intake ports prior to a cold start.

A seat filter is used with what type of system?

Heated steering wheels to keep the air around the driver free from dust and pollen.

What are the differences among IAT, OAT, HOAT, and PHOAT coolants

IAT contains silicate and phosphates and is used in vehicles older than 1996. OAT, HOAT, and PHOAT are used in many vehicles and include their own additive package.

Which sensor might use an aspirator tube?

Inside vehicle temperature

When retrofitting a system from R-12 to R-134a, what is required to be done?

Install a label, convert the fittings, and replace the receiver-drier.

Why should service technicians check a system for the presence of sealant before recovering the refrigerant?

It can harm the recovery machine, it can contaminate the refrigerant that is stored in the recovery container, it can damage a refrigerant identifier.

If the cooling system is low on coolant, what is a common symptom?

Lack of heat from the heater but only when the vehicle is at idle, yet plenty of heat when the engine is operating at highway speeds.

An electrical conductor is an element with __ electrons in its outer orbit.

Less than 4.

As the latent heat of condensation is transferred to the airstream in the condenser, the refrigerant makes the change into a __.

Liquid

The heater control valve, if used, shuts off the coolant flow to the heater core when what setting is selected?

MAX cooling

Reusing old coolant is generally not approved by vehicle manufacturers except __.

Mercedes

Insulators

More than four electrons in their atom's outer orbit.

All of the following statements about hybrid electric vehicle A/C compressors are true, except __.

Most are reciprocating piston designs.

Explain the flow of coolant through the engine and radiator.

Most automotive engines use the coolant pump to circulate coolant through the engine block then cylinder head(s) through the thermostat to the upper portion of the radiator. After losing its heat in the radiator, the coolant is drawn through the lower radiator hose to the opening of the coolant pump where the cycle of events is repeated.

Coolant is hottest in which area?

Near the thermostat.

A module is also known as a __.

Node

What is the normal operating coolant temperature?

Normal operating temperature is within the range of the thermostat rating. A thermostat with a rating of 195 degrees Fahrenheit will start to open at 195 degrees Fahrenheit and will be fully open by 215 degrees Fahrenheit.

Which sensor is also called the ambient air temperature sensor?

Outside air temperature (OAT).

What is the most common type of sun load sensor?

Photodiode

Various electrical switches are used in A/C systems __.

Prevent evaporator icing, protect the compressor, and control fan motors.

The water pump drive belt should be checked for __.

Proper tension, condition, and wear using a gauge.

Like charges __.

Repel

If an insulated wire gets rubbed through a part of the insulation and the wire conductor touches the steel body of a vehicle, the type of failure would be called a __.

Short-to-ground

If two power-side insulated wires were to melt together at the point where the copper conductors touched each other, the type of failure would be called a __.

Short-to-voltage

If a wire repair, such as that made under the hood or under the vehicle, is exposed to the elements, which type of repair should be used?

Solder and adhesive-lined heat shrink or crimp-and seal connectors.

Hybrid electric vehicle A/C compressors:

Some use a belt drive along with an electric motor, some use only an electric motor without a drive belt, non-conductive refrigeration oil must be used with A/C compressors utilizing an electric drive motor.

Technician A says that PTC heaters can be built into a conventional heater core assembly. Technician B says that a PTC heater's electrical resistance will decrease as its temperature increases.

Technician A only

A voltmeter was used to check the coolant and a reading of 0.2 volts with the engine off was measured. A reading of 0.8 volts was measured with the engine running and all electrical accessories turned on. Technician A says that the coolant should be flushed to solve the galvanic activity. Technician B says that the ground wires and connections should be inspected and repaired to solve the electrolysis problem.

Technician B only.

What is the purpose of the coolant system bypass?

The bypass allows coolant to circulate (to prevent hot spots) by the coolant pump within the engine before the thermostat opens. Therefore, the bypass actually is a passage that bypasses the thermostat.

What component cannot be flushed?

The compressor, the condenser, and the receiver-drier cannot be flushed.

What are the sensors used in a typical automatic temperature control (ATC) system?

The fir sensors that are usually used include the outside air temperature (OAT), also called the ambient temperature sensor, and in-vehicle temperature sensor, the discharge air temperature (DAT) sensor, and the evaporator temperature (EVT) sensor and the sun load sensor.

As the percentage of antifreeze in the coolant increases, __.

The freeze point decreases (up to a point).

What is the purpose and function of the heating system?

The heating system uses heat that would normally be wasted (removed by the radiator) to warm the interior of the vehicle.

What is the purpose of the aspirator tube in the in-vehicle temperature sensor section?

The purpose of the aspirator tube is to create a low pressure area to draw air from the interior of the vehicle past the in-vehicle temperature sensor.

Heat transfer is improved from the coolant to the air when __.

The temperature difference is great.

Which statement is true about thermostats?

The temperature marked on the thermostat is the temperature at which the thermostat should start to open.

How does a thermoelectric device (TED) work?

The thermoelectic device consists of positive and negative connections between two ceramic plates. Each ceramic plate has copper fins to allow the transfer of heat to air passing over the device and directed into the seat cushion. When electrical current flows through the module, one side is heated and the other side is cooled reversing the polarity of the current changes the side being heated.

A coolant heat storage tank can keep coolant warm for a maximum of __ days.

Three

Describe how to diagnose a heater problem.

To diagnose a heater problem, first feel the radiator hoses to see that the coolant is hot enough. If the thermostat and coolant level is okay, feel the temperature of the heater hoses; both should be hot.

What is the purpose of a compressor speed sensor?

To let the ECM know if the compressor is turning.

What is the purpose of a flow restrictor, if used?

To slow the coolant velocity as it passes through the heater core, to reduce noise, and to allow for a better heat transfer to the fins/air.

An actuator can be capable of how many positions?

Two, three, variable.

What can be done to prevent air from getting trapped in the cooling system when the coolant is replaced?

Use a coolant exchange machine that draws a vacuum on the system. Open the air bleeder valves while adding coolant.

What are some of the heavy metals that can be present in used coolant?

Used coolant may contain aluminum, lead, and iron which are absorbed into the coolant during engine operation.

What helps prevent water pump cavitation?

Using the specified pressure cap.

Automatic temperature control (ATC) diagnosis includes __.

Verify customer concern, perform a visual inspection, and check for stored diagnostic trouble codes.

Heat is transferred from the hot coolant flowing through the __ to warm the air flowing through the fins of the heater core.

Water tubes

How does a thermoelectric device (TED) work?

When electrical current flows through the module, one side is heated and the other side is cooled.