Maharashtra HSC NSQF Automotive Service Technician (G3) flashcards

31 cards. Read the term and the definition here. The deck at the top of this page is optional.

Class B fire extinguisher

Used for flammable liquids such as petrol, diesel, and solvents. Foam, dry powder, or CO2 is suitable; water must never be applied because it spreads the burning liquid.

5S workplace organisation

Five-step housekeeping method: sort, set in order, shine, standardise, and sustain. In a workshop it reduces lost tools, trip hazards, and time wasted searching.

Lockout tagout procedure

Isolate the energy source, apply a personal lock and tag, verify zero energy, then work. Only the person who applied the lock removes it after the job.

Micrometer least count

Least count equals screw pitch divided by thimble divisions. A 0.5 mm pitch with 50 thimble divisions reads to 0.01 mm, the usual metric workshop resolution.

Vernier calliper least count

Smallest main scale division divided by number of vernier divisions. A 1 mm main division with 50 vernier divisions gives a least count of 0.02 mm.

Feeler gauge use

Set of thin steel blades of known thickness. Used to measure valve clearance, spark plug gap, and ring end gap by finding the blade that enters with slight drag.

Torque wrench handling

Tightens fasteners to a set torque, typically within four percent accuracy. Used only for tightening, never loosening, and reset to lowest setting after use.

Four-stroke cycle order

Intake, compression, power, exhaust. Each cylinder completes one power stroke per two crankshaft revolutions, and the camshaft turns at half crankshaft speed.

Compression ratio formula

Swept volume plus clearance volume, divided by clearance volume. Petrol engines run roughly 9:1 to 12:1; diesel engines run roughly 16:1 to 22:1.

Valve clearance purpose

Small gap between cam lobe base circle and tappet that allows thermal expansion. Too little causes valve burning; too much causes noise and reduced lift.

Diesel compression ignition

Air is compressed to a high ratio, raising temperature above fuel ignition point; fuel is injected near the end of compression and ignites without a spark plug.

Engine displacement calculation

Cylinder cross-sectional area multiplied by stroke and number of cylinders. Bore and stroke must be in the same unit; the result is converted to cubic centimetres.

Clutch pedal free play

Gap, typically 10 to 25 mm, that lets the release bearing clear the pressure plate when the pedal is released. Incorrect free play causes slip or incomplete disengagement.

Torque converter stator

Fixed reaction member between impeller and turbine that redirects fluid flow, multiplying engine torque at low vehicle speed. A lock-up clutch bypasses it at cruise.

Wheel alignment angles

Camber is wheel tilt in front view, caster is steering axis tilt in side view, and toe is the difference in track measured front and rear of the wheels.

Tyre size marking meaning

195/65 R15 means 195 mm section width, sidewall height 65 percent of width, radial construction, and 15 inch rim diameter. Aspect ratio is not a pressure value.

Ohm's law and power

Voltage equals current times resistance. Power equals voltage times current, also current squared times resistance. A 12 V circuit at 5 A uses 60 W.

Lead-acid cell voltage

Each cell produces about 2.1 V nominal, so six cells in series give a 12 V battery. A fully charged open-circuit reading is about 12.6 to 12.8 V.

Alternator charging voltage

Voltage regulator holds output around 13.8 to 14.5 V with the engine running. Below 13.2 V suggests undercharging; above 15 V suggests regulator failure.

Relay terminal numbering

Coil terminals are 85 and 86, supply is 30, normally open load contact is 87, and normally closed contact is 87a. Small coil current switches a large load current.

Parasitic current drain test

With all loads off, connect a multimeter in series at the battery negative and read current. Remove fuses one at a time until the draw drops to normal.

Brake pad minimum thickness

Friction material limit is usually about 2 mm. Pads below the limit are replaced, and discs are checked for runout and minimum thickness against the stamped value.

Coolant 50:50 mixture

Half antifreeze and half water gives freeze protection to about minus 37 degrees Celsius and raises boiling point. Strength is checked with a hydrometer or refractometer.

Cold tyre pressure rule

Tyre pressures are set when tyres are cold, before a run. Hot tyres read higher and setting them hot leads to under-inflation once they cool.

Diagnostic troubleshooting sequence

Verify the complaint, gather information, inspect visually, test, isolate the fault, repair, and verify. A fault code identifies a circuit, not always the failed part.

Blue smoke diagnosis

Blue smoke on acceleration indicates worn piston rings or valve guides. Blue smoke only on start-up after standing points to worn valve stem seals.

Scan tool fault code limits

A code names the affected circuit or system, not the failed component. Confirm with live data, wiring diagram, and physical tests before replacing parts.

Job card contents

Records customer details, vehicle registration, odometer, reported complaint, authorised work, parts, labour, and signatures. It is the legal and technical reference for the job.

Estimate approval rule

Customer must approve the estimate before work begins. Any additional work or cost found during repair requires fresh approval, otherwise the extra bill is disputed.

Break-even quantity formula

Fixed cost divided by selling price per job minus variable cost per job. It gives the minimum number of jobs per month needed to cover all costs.

Active listening in service

Listening without interruption, restating the customer complaint in your own words, and confirming understanding before diagnosis. It reduces misdiagnosis and repeat complaints.