2018 Fleet Tech Challenge

Both Technician A and Technician B are correct. A refractometer can be used to measure freeze protection by measuring the refractive index of a liquid, which can indicate the concentration of antifreeze or coolant in the solution. A hydrometer can also be used to measure freeze protection by measuring the specific gravity of a liquid, which can indicate the concentration of antifreeze or coolant. Both methods are commonly used in automotive and HVAC industries to ensure that the coolant or antifreeze is at the appropriate concentration to prevent freezing.

The pressure cap is the correct answer because it is the cooling system device responsible for maintaining pressure. By raising the boiling point of the coolant, the pressure cap helps prevent the coolant from boiling and ensures that the engine remains at an optimal temperature. The water pump is responsible for circulating the coolant, the thermostat regulates the coolant flow, and the radiator helps dissipate heat, but they do not specifically maintain pressure like the pressure cap does.

The master cylinder should be inspected for internal and external leaks in all of the mentioned scenarios except when the brake pedal is harder to push than normal. This is because a harder brake pedal is usually an indication of a different issue, such as a problem with the brake booster or brake lines, rather than a leak in the master cylinder. In the other scenarios, low brake fluid, a brake warning light, or a low brake pedal reserve height could all be signs of a leak in the master cylinder, which would require inspection.

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The steering knuckle is responsible for connecting the wheels to the suspension and steering system. It is a crucial component that allows the wheels to turn and pivot as directed by the driver's steering input. The steering knuckle is typically attached to the upper and lower control arms, and it houses the wheel hub assembly, which includes the wheel bearings and allows the wheel to rotate smoothly. Overall, the steering knuckle plays a vital role in ensuring proper steering and handling of the vehicle.

Tech B is correct. Bench bleeding a master cylinder does make bleeding the brakes on the vehicle easier. Bench bleeding involves filling the master cylinder with brake fluid and then using a tool or method to push the fluid through the cylinder, removing any air bubbles. This ensures that when the master cylinder is installed in the vehicle, there is no air trapped inside, which would otherwise need to be bled out of the brake lines. By bench bleeding, the technician can save time and effort during the brake replacement process.

Both Technicians A and B are correct. An amp reading substantially below specifications in a charging system output test can be caused by open diodes or a faulty regulator. Open diodes can prevent the proper flow of current, leading to a lower amp reading. Similarly, a faulty regulator can fail to regulate the charging system properly, resulting in a lower amp reading. Therefore, both Technician A and Technician B are correct in their explanations.

Technician A is correct. A starter that clicks once when turning the key to the crank position could be caused by worn solenoid contacts. The solenoid is responsible for engaging the starter motor when the ignition key is turned. If the contacts in the solenoid become worn, it can result in a single click sound instead of the starter motor engaging and turning the engine over.

When measuring voltage with a voltmeter, the red lead is typically connected to the "Volt/Ohms" slot and the black lead is connected to the "Common" slot. This configuration allows for accurate voltage measurements to be taken. Placing the red lead in the "Amps" slot and the black lead in the "Neg" slot is incorrect because the "Amps" slot is used for measuring current, not voltage. Similarly, placing the red lead in the "Pos" slot and the black lead in the "Neg" slot is incorrect because these slots are typically used for power supply connections, not voltage measurements.

Technician B is correct. When checking air pressure, it is important to refer to the specifications on the tire placard, which is usually located on the driver's door, door pillar, or glove compartment lid. This placard provides the recommended air pressure for the specific vehicle, as determined by the manufacturer. The tire sidewall information may provide the maximum allowable pressure for the tire, but it does not necessarily reflect the recommended pressure for the vehicle.

A lean oxygen sensor signal indicates that there is a higher amount of oxygen in the exhaust gases, which suggests that the air-fuel mixture is not rich enough. When this is combined with a large increase in fuel trim, it indicates that the engine control module is trying to compensate for a fuel delivery problem by increasing the amount of fuel being injected into the engine. Therefore, the correct answer is that the vehicle has a fuel delivery problem.

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Tech A is correct because disc brake pads do require higher application force than drum brake shoes. This is because disc brakes work by squeezing brake pads against a rotor, whereas drum brakes work by pushing brake shoes against the inside of a drum. The design of disc brakes allows for better heat dissipation and more efficient braking, but it also requires more force to apply the brakes. On the other hand, Tech B's statement about disc brakes being self-energizing is incorrect and not related to the comparison between disc brakes and drum brakes.

Both Technician A and B are correct. Amperage is indeed the amount of electrons flowing in a circuit, while voltage is the amount of force or energy in a circuit. Amperage measures the current, or the rate of flow of electric charge, while voltage measures the potential difference or the electrical pressure that drives the flow of electrons. Therefore, both technicians have provided accurate descriptions of these electrical concepts.

Tech B is correct. The alternator output circuit voltage drop should be checked with the charging system under a heavy load. This is important because a heavy load can cause a higher voltage drop in the circuit, indicating potential issues with the alternator or other components. Tech A's statement about the rectifier assembly controlling the output of the alternator is not relevant to the question.

Technician B is correct. During a voltage drop test, the engine should be at the specified rpm and the battery should be loaded down so that the alternator puts out maximum current flow. This is because the purpose of the voltage drop test is to check for any excessive resistance in the circuit. By loading down the battery and increasing the current flow, any potential voltage drops across resistance points in the circuit can be identified. Technician A's statement that the voltage drop should be approximately 12.0 volts is incorrect, as the actual voltage drop will depend on the specific circuit and its components.

Technician A is correct. Lug nuts must be torqued to specifications in order to ensure proper and even distribution of force on the wheel. This helps to prevent the wheel from coming loose while driving and ensures the safety of the vehicle. Tightening lug nuts in a random sequence, as suggested by Technician B, can lead to uneven torque and potentially cause the wheel to become loose over time. Therefore, it is important to follow the specified torque sequence when tightening lug nuts.

When attempting a repair on a damaged tire, all of the given statements are true except for the statement that a tire plug by itself is an acceptable repair. A tire plug is not considered a permanent or reliable repair method for a damaged tire. It is recommended to use a combination of a patch and a plug to ensure a proper and long-lasting repair. A tire plug alone may not adequately seal the puncture and can lead to air leaks or further damage to the tire.

Oxygen sensors compare the amount of oxygen in the exhaust gas to the outside air. This is because oxygen sensors are used to measure the oxygen content in the exhaust gas, which helps determine the fuel-to-air ratio in the combustion process. By comparing the oxygen levels in the exhaust gas to the oxygen levels in the outside air, the sensor can provide feedback to the engine control unit to adjust the fuel injection and optimize the combustion process.

Unburned gasoline vapors contain hydrocarbons (HCs). Hydrocarbons are a type of pollutant that are released into the atmosphere when gasoline is not fully burned. These hydrocarbons contribute to air pollution and can react with other pollutants to form smog. They are harmful to human health and the environment.

Tech B is correct. In tire size designations, the "P" actually stands for "passenger" and indicates that the tire is designed for use on passenger vehicles. The "T" in "T135R16" refers to a temporary spare tire.

Tech B is correct. A service brake pedal that does not return causes the brake lights to stay on. When the brake pedal is pressed, it activates a switch that turns on the brake lights. If the pedal does not return all the way, the switch remains engaged, keeping the brake lights on. On the other hand, Tech A is incorrect because a service brake pedal that does not return all the way does not cause the brake warning light on the instrument panel to stay on. The brake warning light typically indicates issues with the braking system, such as low brake fluid or a malfunctioning brake system component.

Neither Tech A nor Tech B is correct. A cleaned-up self-adjuster cannot be installed on either side of the vehicle because self-adjusters are specific to the brake assembly they are designed for and cannot be interchanged. Additionally, grease seals are not meant to be reusable as they are designed to prevent the entry of contaminants and should be replaced whenever the brake components are serviced.

Tech B is correct. A voltage drop can be used to determine if there is unwanted resistance in a circuit. When there is unwanted resistance, it causes a decrease in voltage across the circuit components, resulting in a voltage drop. By measuring the voltage drop, one can identify if there are any issues with resistance in the circuit. On the other hand, Tech A's statement is incorrect. A voltage drop on the ground side of a bulb can indeed affect its brightness as it indicates a decrease in voltage reaching the bulb, leading to a potential decrease in its brightness.

Both Techs A and B are correct. Tech A is correct in stating that a static imbalance condition is centered within the width of the tire. This means that the weight distribution is unevenly distributed across the tire's width, causing vibration. Tech B is correct in stating that a dynamic imbalance condition can be anywhere within the width of the tire. This means that the tire may have uneven weight distribution that changes as it rotates, leading to vibration at different points along the tire's width.

Tech B is correct. Front wheel toe should be adjusted after front wheel caster and camber. Caster and camber are the angles that determine the vertical alignment and tilt of the wheels, while toe refers to the angle at which the wheels point inward or outward when viewed from above. Adjusting the caster and camber first ensures that the wheels are properly aligned vertically, and then the toe can be adjusted to ensure proper alignment horizontally. Therefore, Tech B's sequence of adjustments is the correct order.

Tech A is correct. To read amperage, the meter must be hooked up in series in a circuit. This means that the meter is placed in the path of the current flow, with one lead connected to the input side of the load and the other lead connected to the output side. This allows the meter to measure the current flowing through the circuit accurately. Tech B's statement is incorrect because placing one lead on the input side and the other lead on the output side of the load would not provide an accurate measurement of the amperage.

Neither Technician A nor Technician B is correct. The current carrying capacity of a wire is determined by its gauge, with a lower gauge number indicating a larger wire size and higher current carrying capacity. Therefore, 8 AWG wire carries more current than 12 AWG wire. Additionally, while copper is a good conductor of electricity, the current carrying capacity also depends on factors such as wire length, temperature, and insulation.

The components that follow the road contours, such as wheels, tires, axles, and outboard brake assemblies are considered "unsprung weight" because they are not supported by the suspension system of the vehicle. This weight directly impacts the vehicle's handling and ride quality as it is not absorbed by the suspension, leading to a more rigid and bumpy ride.

Tech A is correct. Camber refers to the angle of the wheels when viewed from the front or rear of the vehicle. Positive camber means the top of the wheels tilt outward, while negative camber means the top of the wheels tilt inward. When a vehicle has positive camber, it tends to pull toward the side with the most positive camber. Therefore, Tech A is correct in stating that a vehicle will tend to pull toward the side with the most positive camber. Tech B's definition of camber is incorrect as it describes caster, which is the forward and backward tilt of the steering axis.

Neither Tech A nor Tech B is correct. A sinking brake pedal can be an indication of a faulty vacuum booster, but it can also be caused by other issues such as air in the brake lines or a worn-out master cylinder. Additionally, the master cylinder can have both external and internal leaks. Therefore, both Tech A and Tech B are incorrect in their statements.

Tech B is correct. In a series circuit, the current flow is the same in each resistor. This is because there is only one path for the current to flow through, and the current is not divided or split between the resistors. Therefore, the current that enters one resistor is the same current that exits the other resistors in the circuit.

Both Technician A and Technician B are correct. Some tire pressure monitoring systems (TPMS) do have a sensor mounted in each wheel rim, while others use the wheel speed sensors in the ABS system to detect tires with low pressure.

The Ackermann principle is applied in steering geometry to navigate a corner without scrubbing. Scrubbing occurs when the inside and outside wheels of a vehicle have different turning radii, causing the tires to slide across the road surface. By implementing the Ackermann principle, the steering system is designed in such a way that the inside and outside wheels turn at different angles during a turn, allowing them to follow their respective radii. This reduces the scrubbing effect and ensures that the tires maintain proper traction, resulting in smoother cornering without excessive tire wear.

Neither Tech A nor Tech B is correct. The correct answer is that clock springs are not used to return the steering wheel to its centered position. Clock springs are actually used to maintain electrical connections for components such as the airbag, horn, and cruise control while allowing the steering wheel to turn. The steering wheel is typically centered by the vehicle's alignment system, not the clock spring.

Tech B is correct. When unloading a MacPherson strut suspension with only a lower control arm, it is recommended to raise the vehicle by the frame and allow the suspension to hang free. This is because the MacPherson strut suspension does not have an upper control arm, so there is no need to place a wood block between the upper control arm and the frame.

Tech A is correct. To read amperage, the meter must be hooked up in series in a circuit. This means that the meter is connected in line with the current flow, allowing it to measure the current passing through the circuit. Tech B's suggestion of placing one lead of the ammeter on the input side of the load and the other lead on the output side of the load would not accurately measure the amperage in the circuit.

Tech B is correct. Tires are indeed marked with a date code listing the date they were manufactured. This date code typically consists of four digits, where the first two digits represent the week of the year and the last two digits represent the year itself. Tires with a three-digit date code are considered too old to be safely in service because they were manufactured prior to the year 2000. These tires may have degraded over time and are more prone to failure, making them unsafe for use on the road.

The voltage regulator in the charging system controls the strength of the rotating magnetic field (rotor). It regulates the voltage output of the alternator by adjusting the amount of current flowing through the rotor. This, in turn, controls the strength of the magnetic field produced by the rotor, which is essential for generating electricity in the alternator. By regulating the voltage, the voltage regulator ensures that the electrical system receives a steady and stable supply of power.

DOT 5 brake fluid is known for its silicone-based formula, which makes it less harmful to paint compared to DOT 3 and DOT 4 fluids. However, this type of fluid is not suitable for vehicles equipped with an anti-lock braking system (ABS). Additionally, DOT 5 brake fluid is not hygroscopic, meaning it does not absorb water. Therefore, the correct answer is that it absorbs water.

Technician B is correct. In a four-stroke engine, it takes four strokes to complete a cycle: intake, compression, power, and exhaust. Only one of these strokes, the power stroke, delivers power to the crankshaft. Technician A is incorrect in stating that it takes only two strokes to complete a cycle.

The "W" in 5W30 engine oil stands for Winter. This indicates the oil's viscosity or thickness at low temperatures. The number before the "W" (5 in this case) represents the oil's viscosity at colder temperatures, while the number after the "W" (30 in this case) represents the viscosity at higher temperatures. The "W" designation ensures that the oil flows properly during cold starts and provides adequate lubrication in winter conditions.

Both Tech A and Tech B are correct. A loaded ball joint does support the weight of the vehicle, as it is designed to carry the load and provide a pivot point for the suspension. On the other hand, in a MacPherson strut suspension, the ball joint is a follower joint, meaning it follows the movement of the suspension components and does not directly bear the weight of the vehicle. Therefore, both statements are true in their respective contexts.

Neither Tech A nor Tech B is correct. According to Ohm's Law, the relationship between voltage, current, and resistance is given by the equation V = I * R, where V is voltage, I is current, and R is resistance. If resistance stays the same and voltage goes up, the current will also go up, not down as Tech A suggests. Similarly, if voltage stays the same and resistance goes down, the current will increase, not decrease as Tech B claims.

Tech B is correct. A voltage drop of .8 volts on a 12V starter ground circuit is not within specifications. This indicates a high resistance in the circuit, which can cause the starter to draw more current. A spun main bearing in the engine can cause excessive friction and resistance, leading to higher starter draw current. Therefore, both Tech A and Tech B are not correct, and the correct answer is Tech B.

An excess of electrons will give the atom a negative charge because electrons have a negative charge. When an atom gains extra electrons, the number of negatively charged electrons exceeds the number of positively charged protons in the nucleus, resulting in an overall negative charge for the atom.

Roll refers to the movement of a vehicle around an imaginary line drawn down the center from front to back. This movement involves the vehicle tilting or leaning to one side, like a boat rocking from side to side. Yaw refers to the movement of the vehicle around a vertical axis, like when the vehicle turns left or right. Pitch refers to the movement of the vehicle around a lateral axis, like when the front of the vehicle moves up or down. Rock is not a term used to describe the movement of a vehicle.

Technician B is correct. Disc brake rotor thickness variation is indeed measured with a micrometer. This tool is used to measure the thickness of the rotor at multiple points to ensure that it is within the manufacturer's specified tolerance. If the thickness variation exceeds the allowable limit, the rotor may need to be replaced. Technician A's statement about reusing rotors as long as the surface is machined smooth is not accurate because rotor thickness variation is an important factor in determining their usability.

The correct answer is 24. This can be calculated using Ohm's law, which states that the current flowing through a resistor is equal to the voltage across the resistor divided by the resistance. In this case, the voltage is 12 volts and the resistance is 0.5 ohms. Therefore, the current flowing through the resistor is 12 volts divided by 0.5 ohms, which equals 24 amps.

Technician B is correct. A higher than normal starter draw amperage reading can be caused by shorted field windings in the starter. Excessive resistance on the starter ground circuit would not cause a higher amperage reading.