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Red Seal Truck and Transport Mechanic study materials
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Red Seal Truck and Transport Mechanic practice questions

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Question 1Occupational Skills (safety, tools, documentation, communication, workflow)

A technician is grinding a frame rail with an angle grinder. Which eye protection practice meets the requirement?

  1. A welding helmet with the lens raised
  2. Safety glasses plus a face shield Correct answer.
  3. Prescription eyeglasses on their own
  4. A ball cap with the brim pulled down

Explanation

Grinding throws high-velocity particles that can travel around the sides and over the top of primary eye protection, so a face shield is worn over impact-rated safety glasses. Prescription eyewear and headwear do not provide impact protection.

Question 2Occupational Skills (safety, tools, documentation, communication, workflow)

A truck is raised with a hydraulic floor jack so the technician can inspect the driveline. What must be done before any part of the body goes under the vehicle?

  1. Chock the wheels and leave the jack handle in place
  2. Place a block of wood between the jack and the frame
  3. Keep one hand on the jack release valve
  4. Lower the vehicle onto rated jack stands Correct answer.

Explanation

A hydraulic jack can bleed down without warning, so the load must be transferred to stands rated for the vehicle weight before anyone works underneath. Chocking and blocking do not provide reliable mechanical support.

Question 3Occupational Skills (safety, tools, documentation, communication, workflow)

A small gasoline fire starts at a fuel spill in the shop. Which extinguisher class is correct for this fire?

  1. Class A
  2. Class D
  3. Class B Correct answer.
  4. Class C

Explanation

Class B extinguishers are rated for flammable liquids such as gasoline, diesel and solvents. The other classes cover ordinary combustibles, energized electrical equipment and combustible metals.

Question 4Occupational Skills (safety, tools, documentation, communication, workflow)

A technician must move a 40 kg brake drum from a bench to a cart. Which technique best reduces the risk of back injury?

  1. Twist at the waist while lifting to save steps
  2. Bend the knees, keep the load close, and get help Correct answer.
  3. Hold the drum at arm's length to keep it clear of the body
  4. Bend at the waist and keep the legs straight

Explanation

Keeping the load close to the body and lifting with the leg muscles reduces the compressive and shear loads on the lower back, and a load of this size should be moved with a mechanical aid or a second person. Twisting while loaded is a common cause of disc injury.

Question 5Occupational Skills (safety, tools, documentation, communication, workflow)

Before servicing the hydraulic lift system on a refuse truck, what is the correct lockout procedure?

  1. Leave the engine idling and ask a co-worker to watch the control levers
  2. Stop the engine, remove the key, tag out, relieve stored pressure Correct answer.
  3. Place a warning cone beside the truck and proceed with repairs
  4. Disconnect the battery ground cable and begin work right away

Explanation

Lockout means isolating the energy source, removing and retaining the key, applying a personal lock and tag, and releasing stored hydraulic and pneumatic pressure before work starts. A second person watching controls is not an acceptable substitute for lockout.

Question 6Occupational Skills (safety, tools, documentation, communication, workflow)

Which document gives the flash point, required personal protective equipment and first-aid measures for a shop chemical?

  1. The product safety data sheet Correct answer.
  2. The vehicle service manual
  3. The supplier's packing slip
  4. The shop's waste manifest

Explanation

WHMIS requires a safety data sheet for every hazardous product, and it covers hazard classification, first aid, firefighting, handling and storage, exposure controls, and physical properties such as flash point. Shipping and repair documents do not carry this information.

Question 7Occupational Skills (safety, tools, documentation, communication, workflow)

After finishing a job with a click-type micrometer torque wrench, what is the correct storage practice?

  1. Return it to its lowest scale setting Correct answer.
  2. Store it wrapped in electrical tape
  3. Leave it set at the torque last used
  4. Oil the click mechanism before storing

Explanation

Leaving a micrometer-type wrench set at a working value keeps the internal spring compressed, which causes calibration drift over time. The wrench should be wound back to its lowest setting and stored in a case away from drops and moisture.

Question 8Occupational Skills (safety, tools, documentation, communication, workflow)

A technician finds worn front brake pads during a scheduled service. What is the correct documentation practice?

  1. Record it only after the customer approves the extra repair work
  2. Document the finding and recommendation on the work order Correct answer.
  3. Mention it to the customer verbally at pickup
  4. Note it on the shop whiteboard for the next shift

Explanation

Findings and measurements belong on the work order so there is a permanent record for the customer, the shop and any warranty claim, and so the recommendation can be presented for approval. Informal or verbal notes are easily lost.

Question 9Occupational Skills (safety, tools, documentation, communication, workflow)

Before starting a repair on a truck parked in the yard, what should the technician do first?

  1. Collect the required parts from the crib
  2. Warm the engine to operating temperature
  3. Raise the hood and remove the keys
  4. Complete a field-level hazard assessment Correct answer.

Explanation

A field-level hazard assessment identifies traffic, ground conditions, overhead hazards, stored energy and weather, and records the controls before work begins. It is repeated whenever conditions change during the job.

Question 10Occupational Skills (safety, tools, documentation, communication, workflow)

How should full oxygen and acetylene cylinders be stored in the shop?

  1. Standing free with regulators left attached for quick use
  2. Chained together in a horizontal rack near a heater
  3. Laid flat on the floor to prevent tipping
  4. Upright, secured, with valve protection caps installed Correct answer.

Explanation

Compressed gas cylinders are stored upright and secured against tipping, with valve caps on, away from heat, and with fuel gas separated from oxygen. Regulators are removed for storage so a damaged valve cannot release gas.

Question 11Occupational Skills (safety, tools, documentation, communication, workflow)

During a repair, a technician finds a cracked exhaust hanger that the customer did not authorize. What is the best action?

  1. Ask the parts driver to decide on the customer's behalf
  2. Explain the finding and get approval before repairing it Correct answer.
  3. Weld it and add the cost to the invoice without discussion
  4. Ignore it because the original work order did not list it

Explanation

The customer authorizes the scope of work, so added repairs require informed approval of both the reason and the cost before they are performed. Documenting the conversation also protects the shop if the customer declines the work.

Question 12Occupational Skills (safety, tools, documentation, communication, workflow)

A two-leg nylon web sling shows a deep cut through the outer cover and a burn mark. What is the correct action?

  1. Use it at half the rated capacity for light loads
  2. Remove it from service and destroy or tag it as defective Correct answer.
  3. Tape the cut and continue using the sling
  4. Use it only in a basket hitch so the damage sits on top

Explanation

A sling with a cut through the cover or heat damage is permanently removed from service, because load-bearing yarns may be severed or melted and the rated capacity no longer applies. It must be tagged or destroyed so it cannot be returned to the rack.

Question 13Occupational Skills (safety, tools, documentation, communication, workflow)

A technician is repairing the A/C system on a truck. What is required before the system is opened?

  1. Vent the charge slowly to the atmosphere
  2. Cap the lines and let the charge escape
  3. Recover the refrigerant into an approved cylinder Correct answer.
  4. Fill the system with nitrogen to push the charge out

Explanation

Refrigerant must be recovered with approved equipment into a recovery cylinder before the system is opened, and it may never be vented to atmosphere. Recovery cylinders are not filled beyond about 80 percent to allow for liquid expansion.

Question 14Occupational Skills (safety, tools, documentation, communication, workflow)

A 0-25 mm outside micrometer reads 0.02 mm with the spindle closed against the anvil. What does this indicate?

  1. Zero error exists; correct readings or recalibrate Correct answer.
  2. The tool is within normal zero tolerance
  3. The friction thimble needs more closing pressure
  4. The thimble has been set to the inch scale by mistake

Explanation

With clean faces closed, a micrometer should read zero; a reading of 0.02 mm is a zero error that must be applied as a correction to every measurement or adjusted out before use. A tool with zero error is set aside until it is recalibrated.

Question 15Engine and Engine Support Systems

In a four-stroke diesel engine, what initiates combustion?

  1. A spark plug firing near top dead centre
  2. Residual exhaust gases igniting the intake charge
  3. A glow plug igniting a pre-mixed air-fuel charge
  4. Heat from compressed air igniting injected fuel Correct answer.

Explanation

A diesel engine uses a high compression ratio to heat the intake air above the fuel's ignition temperature. Fuel is injected near the end of the compression stroke and self-ignites from that heat. A spark plug is not used for main combustion in a direct-injection diesel.

Question 16Engine and Engine Support Systems

What is the primary purpose of valve lash clearance in a diesel engine?

  1. To increase valve lift at high engine speed
  2. To reduce oil flow to the valve guides
  3. To allow for thermal expansion so valves seat when hot Correct answer.
  4. To keep the rocker arms in constant contact with the valve stems

Explanation

Valvetrain components expand as the engine reaches operating temperature. Correct valve lash allows that expansion without holding a valve off its seat. If clearance is incorrect, valve timing and sealing are affected.

Question 17Engine and Engine Support Systems

What is the function of the thermostat in an engine cooling system?

  1. It senses coolant pressure and opens the radiator cap
  2. It filters debris from the coolant before it reaches the radiator
  3. It regulates coolant flow to maintain operating temperature Correct answer.
  4. It circulates coolant through the radiator at all times

Explanation

The thermostat opens and closes with coolant temperature to control flow to the radiator. This keeps the engine within its designed operating range. It does not pump coolant or filter it.

Question 18Engine and Engine Support Systems

What does the pressure cap on a closed cooling system do?

  1. It raises the coolant boiling point above atmospheric pressure Correct answer.
  2. It prevents coolant from expanding into the overflow bottle
  3. It increases coolant flow through the heater core
  4. It vents air from the system during normal operation

Explanation

A pressure cap holds system pressure above atmospheric pressure, which raises the boiling point of the coolant. This allows higher operating temperatures without boil-over. The cap also has a relief valve to protect the system.

Question 19Engine and Engine Support Systems

What is the main function of engine mounts in a truck chassis?

  1. They support the weight of the radiator and charge air cooler
  2. They lock the engine rigidly to the frame to prevent any movement
  3. They align the crankshaft with the transmission input shaft
  4. They isolate vibration and allow controlled movement under torque Correct answer.

Explanation

Engine mounts cushion vibration and allow limited movement as the engine reacts to torque. They also help keep the engine aligned with the driveline without transmitting harsh vibration to the frame. They are not rigid restraints.

Question 20Engine and Engine Support Systems

A restriction indicator on the engine air intake indicates what?

  1. When the air filter has reached its service limit Correct answer.
  2. The boost pressure produced by the turbocharger
  3. The temperature of the charge air entering the manifold
  4. The amount of crankcase blowby entering the intake

Explanation

An intake restriction indicator monitors vacuum between the air filter and the turbocharger or engine. When restriction reaches a set value, the indicator shows that the filter is due for service. It does not measure boost or temperature.

Question 21Engine and Engine Support Systems

What is the purpose of an automatic serpentine belt tensioner?

  1. It measures belt slip and signals the ECM
  2. It increases belt speed at higher engine rpm
  3. It maintains belt tension as the belt wears and stretches Correct answer.
  4. It disengages the belt when the engine is stopped

Explanation

A spring-loaded automatic tensioner keeps a consistent load on the serpentine belt as it stretches and wears. This prevents slip without overloading bearings. It does not change belt speed or signal the ECM.

Question 22Engine and Engine Support Systems

What is the function of the ring gear on a diesel engine flywheel?

  1. It balances the crankshaft at high speed
  2. It drives the camshaft through a gear train
  3. It provides a mounting surface for the clutch pressure plate
  4. It has teeth for the starter pinion to crank the engine Correct answer.

Explanation

The starter motor pinion engages the flywheel ring gear teeth to rotate the crankshaft during cranking. The ring gear is separate from the friction surface used by the clutch. Engine balance is handled by the crankshaft and damper.

Question 23Engine and Engine Support Systems

A turbocharger wastegate actuator is stuck closed. What is the most likely result?

  1. Boost pressure rises above the specified limit Correct answer.
  2. The turbocharger produces no boost at any speed
  3. The compressor wheel stops rotating at idle
  4. Exhaust gas temperature drops sharply under load

Explanation

The wastegate bypasses exhaust gas around the turbine to limit boost. If it remains closed, all exhaust flow drives the turbine and boost can exceed the specified limit, risking overboost and engine damage.

Question 24Engine and Engine Support Systems

A cylinder head gasket leaks coolant into a cylinder. Which symptom is most likely?

  1. White exhaust smoke and falling coolant level Correct answer.
  2. A steady increase in oil pressure at idle
  3. Blue smoke only at startup after sitting
  4. Fuel dilution of the engine oil

Explanation

Coolant entering the combustion chamber is vaporized and leaves as white smoke or steam, and the cooling system level drops. The leak can also pressurize the cooling system and cause overheating.

Question 25Engine and Engine Support Systems

A warm diesel engine shows low oil pressure at idle that rises with engine speed. Which cause is most likely?

  1. Worn main and connecting rod bearings Correct answer.
  2. A stuck-open oil pressure relief valve at all speeds
  3. A clogged oil filter bypass valve stuck closed
  4. Too much oil in the crankcase

Explanation

Worn bearings increase oil clearance, so oil escapes faster, especially at low speed when pump output is low. Pressure rises as engine speed increases but may remain below specification. A stuck-open relief valve usually lowers pressure at all speeds.

Question 26Engine and Engine Support Systems

What is the effect of a restricted charge air cooler on engine performance?

  1. Lower exhaust gas temperature and reduced NOx
  2. Reduced power and higher intake air temperature Correct answer.
  3. Higher intake air density and increased power
  4. Increased coolant flow through the radiator

Explanation

The charge air cooler lowers intake air temperature to increase air density. If it is restricted or fouled, the air stays hot and less dense, so the engine produces less power and may smoke.

Question 27Engine and Engine Support Systems

Excessive crankcase blowby on a diesel engine usually indicates what?

  1. A faulty thermostat staying open
  2. A leaking exhaust manifold gasket
  3. An overfilled cooling system
  4. Worn piston rings or cylinder liners Correct answer.

Explanation

Blowby is combustion gas that escapes past the piston rings into the crankcase. Excessive blowby indicates poor ring-to-liner sealing, often from worn rings, worn liners, or a damaged piston.

Question 28Engine and Engine Support Systems

How does an exhaust brake slow a heavy truck?

  1. It applies the service brakes through the ECM
  2. It closes the intake throttle to starve the engine of air
  3. It retards camshaft timing to reduce engine power
  4. It restricts exhaust flow, creating backpressure that opposes piston travel Correct answer.

Explanation

An exhaust brake closes a valve in the exhaust stream, raising exhaust backpressure. That pressure resists the pistons during the exhaust stroke and provides braking effort. It does not apply the service brakes.

Question 29Engine and Engine Support Systems

An EGR cooler has an internal coolant leak. Which symptom is most likely?

  1. Black smoke and increased boost pressure
  2. A loud exhaust leak at the manifold
  3. Engine oil level rising with fuel dilution
  4. Coolant loss with white smoke from the exhaust Correct answer.

Explanation

An internal EGR cooler leak allows coolant into the exhaust or intake path, where it vaporizes as white smoke. Coolant is also lost from the cooling system. Combustion symptoms alone do not confirm this leak.

Question 30Engine and Engine Support Systems

A diesel injector nozzle has a pop pressure below specification. What is the most likely effect?

  1. The injector delivers fuel earlier and increases power
  2. The injector sprays a finer mist and reduces emissions
  3. Cylinder pressure rises and the engine detonates
  4. Fuel atomization is poor, causing rough running and black smoke Correct answer.

Explanation

Nozzle pop pressure determines when the injector opens and how fuel is atomized. If it is too low, the injector opens early and the spray pattern deteriorates, causing rough running, misfire, and black smoke.

Question 31Engine and Engine Support Systems

Why does the ECM derate a diesel engine when coolant temperature is too high?

  1. To reduce heat load and protect the engine from damage Correct answer.
  2. To increase coolant flow through the radiator
  3. To raise oil pressure for the turbocharger
  4. To test the cooling fan clutch operation

Explanation

When coolant temperature exceeds safe limits, the ECM reduces fuel delivery to lower heat rejection and protect the engine. Derate is a protective strategy, not a test of cooling system components.

Question 32Engine and Engine Support Systems

What can happen if valve lash is adjusted too tight on a diesel engine?

  1. The valves may not seat fully and can burn Correct answer.
  2. Oil pressure at the rocker arms increases
  3. The pushrods become too short for the lifters
  4. The valves open later and lift decreases

Explanation

Too little valve lash holds the valve slightly off its seat when the engine is hot. Compression is lost and hot combustion gas can escape past the valve face, leading to burning and valve damage.

Question 33Engine and Engine Support Systems

A diesel engine has a ticking noise that is loudest when cold and fades as it warms, with soot stains at the manifold. What is the most likely cause?

  1. A leaking exhaust manifold gasket Correct answer.
  2. An injector with a high pop pressure
  3. A loose serpentine belt
  4. A worn turbocharger bearing

Explanation

An exhaust manifold gasket leak allows hot exhaust gas to escape, producing a sharp ticking noise that often changes as components expand with heat. Soot stains at the joint support the diagnosis.

Question 34Engine and Engine Support Systems

What is plastigauge used to measure during an engine overhaul?

  1. Cylinder liner protrusion above the block deck
  2. Valve stem-to-guide clearance
  3. Piston ring end gap in the bore
  4. Journal-to-bearing clearance Correct answer.

Explanation

Plastigauge is a crushable plastic strip placed across a bearing journal and torqued to specification. Its compressed width indicates the oil clearance between the journal and bearing. It is not used for ring gap or liner protrusion.

Question 35Engine and Engine Support Systems

Cylinder liner protrusion is measured below specification on a wet-liner engine. What is the most likely consequence?

  1. The injector will protrude too far into the combustion chamber
  2. The head gasket may leak coolant or lose compression Correct answer.
  3. The piston rings will not seal against the liner
  4. The crankshaft end play will increase

Explanation

Liner protrusion creates clamping load on the head gasket when the head is torqued. If protrusion is too low, the gasket may not seal combustion pressure or coolant passages. Ring sealing and crankshaft end play are separate concerns.

Question 36Engine and Engine Support Systems

What happens if piston ring end gap is set too small?

  1. The ring will not seal and excessive blowby results
  2. The ring will rotate on the piston and damage the pin
  3. The ring ends butt when hot and the ring can break Correct answer.
  4. The ring will wear the cylinder liner faster at the top

Explanation

Rings expand as they heat up, so the end gap must allow for that growth. If the gap is too small, the ends butt together and the ring can scuff the bore or break.

Question 37Engine and Engine Support Systems

In a diesel engine with overhead valve adjustment, what does valve seat recession cause?

  1. Valve lash decreases and compression may be lost Correct answer.
  2. The valve guides wear faster and oil consumption rises
  3. Valve lash increases and the valve opens later
  4. The valve springs lose tension and float at low speed

Explanation

Valve seat recession means the valve sinks deeper into the head, so the stem tip moves closer to the rocker arm. Valve lash decreases and the valve may be held off its seat, causing compression loss.

Question 38Engine and Engine Support Systems

How can a failed elastomeric crankshaft vibration damper affect engine operation?

  1. It advances injection timing by turning the crankshaft
  2. It increases oil pressure by driving the oil pump faster
  3. The outer ring can slip, making timing marks inaccurate and increasing vibration Correct answer.
  4. It disengages the fan clutch at high speed

Explanation

The damper's outer ring is bonded to the hub through an elastomer. If the bond fails, the ring can slip, so the timing marks no longer accurately indicate crankshaft position and torsional vibration increases.

Question 39Engine and Engine Support Systems

A wet cylinder liner O-ring is leaking coolant into the crankcase. Which symptom would you expect?

  1. Excessive black smoke and low boost pressure
  2. Coolant-contaminated engine oil and a rising oil level Correct answer.
  3. High oil pressure at idle and low oil pressure at speed
  4. A loud knock that disappears when the engine warms

Explanation

Wet liner O-rings seal coolant from the crankcase. A leak allows coolant into the oil, making the oil level rise and giving it a milky or contaminated appearance. Coolant contamination also reduces lubrication.

Question 40Engine and Engine Support Systems

A truck's coolant temperature gauge stays well below normal after a long highway drive in cold weather, and the cab heater output is weak. Which component is the most likely cause?

  1. A radiator cap that does not hold pressure
  2. A water pump with a broken impeller
  3. A thermostat that is stuck closed
  4. A thermostat that is stuck open Correct answer.

Explanation

A thermostat that stays open allows continuous full coolant flow through the radiator, so the engine cannot reach or hold its designed operating temperature and heater output drops. A thermostat stuck closed restricts flow and produces overheating, not an engine that runs cold. Impeller and pressure cap faults also show up as overheating or coolant loss.

Question 41Engine and Engine Support Systems

A driver reports a heavy clunk from under the cab when pulling away from a stop. With the hood raised, the engine can be seen rocking noticeably when torque is applied in gear. Which condition best explains these symptoms?

  1. A leaking exhaust manifold gasket
  2. A failed engine mount Correct answer.
  3. A glazed serpentine belt
  4. A worn driveshaft universal joint

Explanation

Engine mounts anchor the block to the frame and absorb torque reaction; when one fails, the engine lifts or rocks under load and the housing contacts the frame, producing a clunk on torque reversal. A universal joint clunk comes from the driveline and does not make the engine move visibly. Belt glazing and exhaust leaks cause noise or performance complaints but not engine movement.

Question 42Engine and Engine Support Systems

A highway tractor with a viscous fan drive overheats while pulling hard at low road speed but returns to normal temperature once it reaches highway speed. Which is the most likely cause?

  1. The coolant temperature sensor is reading high
  2. The thermostat is stuck open
  3. The radiator core is internally restricted
  4. The viscous fan drive is not engaging Correct answer.

Explanation

At low road speed the cooling system depends on the fan to pull air through the radiator; if the viscous drive slips and never engages, airflow falls off and temperature climbs. At highway speed ram air is enough to keep temperature normal, which is why the complaint is speed dependent. A restricted radiator or a stuck-open thermostat would not improve specifically with road speed, and a faulty sensor would not change actual cooling.

Question 43Engine and Engine Support Systems

A diesel engine produces a puff of blue-grey smoke on start-up after sitting and idling for a long period, uses a slight amount of oil, and otherwise runs clean under load. Which is the most likely cause?

  1. A leaking injector nozzle
  2. Worn piston rings
  3. A leaking turbocharger shaft seal
  4. Worn valve stem seals Correct answer.

Explanation

Worn valve stem seals let oil run down the valve guides while the engine sits or idles under high manifold vacuum, producing a puff of oil smoke at start-up that clears once the engine runs. Ring wear typically causes continuous blowby and smoke under load, not a single start-up puff. A turbo seal or leaking injector usually produces smoke that persists at idle or under load.

Question 44Engine and Engine Support Systems

During an engine overhaul, flywheel housing bore runout is measured and found to exceed the manufacturer's specification. If it is not corrected, which outcome is most likely?

  1. Misalignment between the engine and transmission that rapidly wears the clutch or input shaft bearing Correct answer.
  2. Excessive valve lash clearance
  3. High exhaust backpressure
  4. Low engine oil pressure at idle

Explanation

The transmission mounts to the flywheel housing, so excessive runout of its bore tilts the housing relative to the crankshaft axis and misaligns the transmission input shaft with the crankshaft pilot bore. That misalignment loads the clutch disc hub, release bearing and input shaft bearing and can cause vibration and premature failure. Oil pressure, valve lash and exhaust backpressure are set by entirely different systems.

Question 45Electrical and Electronic Systems

A lead-acid battery that has been rested and shows an open-circuit voltage of 12.6 V at 25 °C is best described as:

  1. fully charged Correct answer.
  2. suffering a shorted cell
  3. deeply discharged
  4. about 50% charged

Explanation

A rested lead-acid battery reads about 12.6 V at 100% state of charge, roughly 12.2 V at 50% and 11.9 V or lower when deeply discharged. Open-circuit voltage is only meaningful after surface charge has been removed by a load or a rest period.

Question 46Electrical and Electronic Systems

What is the primary function of a fuse in a truck electrical circuit?

  1. It smooths voltage ripple to the load
  2. It opens the circuit on excess current Correct answer.
  3. It reduces current to the load at all times
  4. It limits the voltage reaching the load

Explanation

A fuse is a sacrificial conductor that melts when circuit current exceeds its rating, protecting the wiring and components from overheating. It has near-zero resistance during normal operation and does not regulate voltage.

Question 47Electrical and Electronic Systems

To measure current flow in a circuit, the meter must be:

  1. placed in series with the circuit Correct answer.
  2. connected from positive to ground
  3. set to the highest resistance range
  4. connected across the load

Explanation

An ammeter must carry the circuit current, so it is connected in series and has very low internal resistance. Connecting it in parallel across a load would short the circuit through the meter.

Question 48Electrical and Electronic Systems

A healthy charging system on a truck at fast idle with accessories off should show approximately:

  1. 10.5 to 11.5 V
  2. 12.0 to 12.6 V
  3. 13.8 to 14.5 V Correct answer.
  4. 15.5 to 16.5 V

Explanation

A properly working alternator holds roughly 13.8 to 14.5 V at fast idle. Readings near battery voltage mean no charge is being produced, while readings above about 15 V indicate overcharging.

Question 49Electrical and Electronic Systems

Three resistors of 3 Ω, 5 Ω and 7 Ω are connected in series. What is the total resistance?

  1. 1.5 Ω
  2. 5 Ω
  3. 15 Ω Correct answer.
  4. 0.68 Ω

Explanation

In a series circuit the same current flows through every resistor and the individual resistances add: 3 + 5 + 7 = 15 Ω.

Question 50Electrical and Electronic Systems

In a standard 7-way trailer connector, the white conductor serves as:

  1. the auxiliary power feed
  2. the stop lamp feed
  3. the left turn feed
  4. the ground circuit Correct answer.

Explanation

The 7-way connector uses white for ground, brown for tail, yellow for left turn, green for right turn, red for stop, black for auxiliary power and blue for electric brakes.