Five free practice questions on cab interior and exterior: block G of the Red Seal 310T Truck and Coach Technician exam, about 5 of its 135 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A driver reports the air-ride seat in a tractor sinks slowly while driving and the compressor cycles more than usual. What is the most likely cause?
- A worn seat belt webbing.
- Worn seat slide tracks.
- A weak or sulfated battery.
- An air leak at the seat.
Show the answer
D. Correct. An air seat is fed from the vehicle's air system through a valve and a bag; a leak at any of them lets the seat sink and consumes air, working the compressor. The RSOS lists air leak on seat among interior cab symptoms and pneumatics and air-powered accessories among components; the leak is found with soapy water with the seat charged and the bag, valve or line repaired or replaced. The reservoir is drained before the seat's air components are opened.
Why not the others
A. Seat belts do not affect the seat's ride height.
B. Track wear affects fore-and-aft movement, not the seat's height or air consumption.
C. The seat's air system is pneumatic; the battery is unrelated.
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During an exterior inspection the technician finds a crack in a coach's cab frame near a suspension mount and several loose fairing fasteners. What is the significance?
- Structural; repair per the OEM.
- Normal ageing of the cab structure.
- A tire balance problem.
- Cosmetic issues only, no action.
Show the answer
A. Correct. The RSOS lists cracks in cab frame and loose fasteners and fairings among exterior cab defects. A cab frame crack at a suspension mount grows under road loads until the mount fails, and loose fairings come off at speed; the crack is repaired according to the manufacturer's procedure (welding and cutting equipment are listed tools, subject to the manufacturer's method and the technician's certification) or the section replaced, and the fairing fasteners are replaced and torqued. Both findings are recorded and the cab is re-inspected after repair.
Why not the others
B. Cracks are never normal; they indicate overload, fatigue or a prior repair failure.
C. Tires are unrelated to cab frame cracks.
D. A cab frame crack is structural, and loose fairings are a road hazard.
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A driver reports the brake pedal on a coach sometimes stays partly down after release, and the brake lights stay on. What should the technician check first?
- The air compressor governor.
- The stop lamp bulbs.
- The driver's seat belt retractor.
- Pedal pivot and brake switch.
Show the answer
D. Correct. A pedal that does not return fully is sticking at its pivot (dry, corroded or worn bushings, a weak return spring) or being held by the treadle valve; the brake switch staying on follows from the pedal's position or from a switch out of adjustment. The RSOS lists sticking pedals among interior cab symptoms, pedal pivot points among components lubricated, and brakes, clutches and brake switches among components adjusted. A pedal that does not release can drag the brakes, so it is corrected before the vehicle returns to service.
Why not the others
A. The compressor supplies air; it does not make the pedal stick.
B. The lamps are doing what the brake switch tells them; they are the symptom, not the cause.
C. Seat belts are unrelated to pedal return.
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A highway tractor's cab air suspension uses a single height control valve near the centre of the rear cab crossmember, feeding both rear air springs through a tee. With the system at 830 kPa (120 psi) the cab sits 25 mm (1 in) lower on the left than on the right, against a manufacturer's limit of 6 mm (0.25 in); a gauge in the shared line reads 410 kPa (60 psi) and both springs pass a soap test. What is the cause?
- Height control valve out of adjustment
- Pressure protection valve opening late
- Collapsed left cab mount or spring seat
- Left rear air spring leaking at the bead
Show the answer
C. Correct. With one valve and a common line both springs see the same 410 kPa, so equal pressure with unequal height means the difference is mechanical: a collapsed rubber mount, bent levelling rod or broken lower spring seat on the low side. NSC 11 rejects an air-suspended cab that tilts to one side and any mount, rod or attachment that is bent, broken or loose. Replace the mount, then reset ride height at the valve.
Why not the others
A. A valve adjustment error moves both springs together, because the one valve feeds both through the shared line; it can leave the whole cab high or low but cannot create a 25 mm side-to-side lean. Reset the valve only after the lean is corrected.
B. The pressure protection valve sits upstream of the height control valve and gates supply to the whole cab circuit; it could leave the cab low on both sides but not lean it. 410 kPa in the shared line proves supply is reaching the springs.
D. The springs share one line, so a leaking left spring would drop pressure and height on both sides together, and both springs passed the soap test. A leak does not explain a one-sided lean with 410 kPa in the line.
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A driver reports a tractor's cab rides rough and sits visibly lower on one rear corner. What should the technician test?
- The trailer's landing gear legs.
- Cab ride height and its air suspension.
- The clutch free-play adjustment.
- The engine's diesel particulate filter.
Show the answer
B. Correct. The RSOS lists cab tilted and rough ride among exterior cab symptoms, checking cab ride height among the tests, and leaking or damaged shocks and valves, worn bushings and failed air bags among defects. A cab air suspension has its own height control valve, air bags and shocks; a leaking bag or a failed or mis-set valve drops one corner and a failed shock makes the ride harsh. Ride height is measured against the manufacturer's value, the bag and valve soaped for leaks, and the shock and bushings inspected; NSC 11 rejects a cab that tilts to one side or sits off its normal height.
Why not the others
A. Landing gear is a trailer item unrelated to the cab.
C. The clutch is unrelated to cab suspension.
D. The aftertreatment system does not affect cab ride.
02Answer key
| Question | Answer | Sub-task |
|---|---|---|
| Q1 | D | Diagnoses interior cab components |
| Q2 | A | Diagnoses exterior cab components |
| Q3 | D | Diagnoses interior cab components |
| Q4 | C | Diagnoses exterior cab components |
| Q5 | B | Diagnoses exterior cab components |
03What block G covers
This block covers the inside and outside of the cab. It includes seats and air-ride seats, pedals and steering columns, dash valves, SRS and air bag safety, window regulators and motors, cab air suspension and ride height, hoods and tilt mechanisms, doors, hinges and strikers, mirrors, wipers, windshields, and headlight aim.
The Red Seal Occupational Standard names this block “Services, diagnoses and repairs cabs”. It carries 3.7% of the exam, about 5 of the 135 questions, split across two tasks. The share column is each task's weight within the block, as the standard publishes it.
| Task and its sub-tasks | Share of block |
|---|---|
| Services, diagnoses and repairs interior cab components Services interior cab components; Diagnoses interior cab components; Repairs interior cab components | 56% |
| Services, diagnoses and repairs exterior cab components Services exterior cab components; Diagnoses exterior cab components; Repairs exterior cab components | 44% |
04What the questions turn on
Release stored energy first
Interior cab work starts with disconnecting power, draining the air reservoirs that feed seats and pneumatic accessories, and waiting for SRS module capacitors to discharge. Air bag modules are pyrotechnic, and SRS work requires the manufacturer's training.
Air leaks around the cab
An air-ride seat that sinks while the compressor cycles more than usual has a leak at the seat's bag, valve or line. A cab sitting low on one corner points to its own air suspension, such as a leaking bag or a failed height valve.
Sticking or heavy pedals
A brake pedal that stays partly down with the brake lights on is sticking at its pivot or being held by the treadle valve. For heavy pedal effort, a force meter compares the effort to the manufacturer's value before parts are condemned.
Windshield and lamp checks
In the wiped area, NSC 11 rejects a windshield crack over 50 mm or a chip over 13 mm. A dim headlight gets a voltage-drop check on its circuit before it is aimed on the screen with headlight adjusting tools.
05The other blocks
The 310T exam has 11 blocks. Each has its own page of free questions:
The 310T Truck and Coach Technician practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.