Maharashtra SSC Automotive Service Technician Pre-Voc/NSQF cheat sheet

Fire classes: A solid combustibles, B flammable liquids, C electrical/gas, D metals; water is banned on B and C, CO2 and dry powder suit C, foam suits B.

PPE order for a workshop: safety goggles, steel-toe shoes, coveralls, ear plugs above 85 dB(A), nitrile gloves for fuels and solvents, welding helmet with shade 10-13.

Exhaust CO is odourless and lethal; run engines only with hose extraction, and treat headache plus dizziness in a bay as CO exposure until proven otherwise.

Jack stands must be rated above the lifted load and placed on level ground; a hydraulic jack alone is a lifting device, never a support.

Battery charging releases hydrogen: no sparks, no smoking, vent the area, and keep acid spill neutraliser (sodium bicarbonate) within reach.

Solvent and paint containers stay closed, are stored away from ignition sources, and used thinner is collected as hazardous waste, never poured into drains.

First aid sequence: make the scene safe, check response and breathing, call emergency services, control bleeding with direct pressure, do not move a suspected spinal injury.

Compressed air must never be used to clean skin or clothing; limit blow-gun pressure and wear eye protection because chips travel at high speed.

Spanner size refers to the across-flats dimension of the fastener; a 13 mm bolt head takes a 13 mm ring spanner, and ring ends are preferred over open ends on tight nuts.

Torque = force x perpendicular distance; a 0.4 m bar with 100 N applied gives 40 N.m, and torque wrenches are accurate only between roughly 20% and 100% of full scale.

Torque-to-yield (stretch) bolts are tightened to a torque plus a specified angle and are replaced, not reused, after removal.

A puller is used for bearings, pulleys and ball joints; never hammer a bearing race, and press or drift only on the interference-fit member.

Feeler gauges measure gaps such as valve clearance and spark plug gap; blade thickness equals the gap when there is a light drag.

Micrometer = sleeve reading + thimble reading; a 0-25 mm micrometer with 0.01 mm thimble divisions reads 0.01 mm per division, with a vernier scale giving 0.001 mm.

A dial indicator with magnetic base measures runout, end play and backlash; plunger travel must be perpendicular to the measured surface.

Special tools are compulsory for timing belts, injector removal and bearing/seal fitting; using a generic chisel or screwdriver as a drift damages sealing surfaces.

Vernier caliper reading = main scale value + (coinciding vernier line x least count); least count = 1 main division / number of vernier divisions, typically 0.02 mm.

Outside micrometer least count is 0.01 mm on the thimble; zero error is checked by closing the anvils and noting any offset, which is added or subtracted from readings.

Cylinder bore is measured with a bore gauge or inside micrometer at three heights and two directions (thrust and axial) to detect taper and ovality.

Cylinder wear limit is judged against the manufacturer's maximum taper and ovality, not against nominal bore alone; reboring needs the next oversize piston.

Crankshaft journal ovality and taper are checked with a micrometer at two positions 90 degrees apart; grinding requires undersize bearings.

Surface finish and cleanliness matter: a 0.001 mm error from dirt under a micrometer anvil is a real measurement error, so wipe the part and the instrument.

Workshop 5S: sort, set in order, shine, standardise, sustain; tools are returned to marked positions and calibrated instruments are stored in cases.

Calibration status is recorded with a sticker and date; an instrument that has been dropped or overloaded is withdrawn from service until rechecked.

Four-stroke cycle order is intake, compression, power, exhaust; the crankshaft turns twice per cycle and the camshaft once, so cam sprocket ratio is 2:1.

Compression ratio = (swept volume + clearance volume) / clearance volume; petrol engines run roughly 9:1 to 12:1, and higher ratios demand higher-octane fuel.

Valve clearance is set cold on most engines with a feeler gauge at the specified clearance; too little clearance causes burnt valves, too much causes noise and reduced lift.

Head bolt tightening follows the maker's sequence, usually from centre outwards in stages, because uneven clamping distorts the head and head gasket.

Timing marks on crank, cam and injection pump must align exactly; one tooth off causes hard starting, poor power or valve-to-piston contact on interference engines.

Oil pressure low at idle with a worn engine points to worn bearings, a stuck relief valve or a clogged pickup; verify with a mechanical gauge before condemning parts.

Coolant thermostat opening temperature and radiator cap pressure rating must match specification; a weak cap lowers boiling point and causes overheating.

Engine overhaul measurement set: bore taper/ovality, piston-to-bore clearance, ring end gap, journal ovality, crankshaft end play and connecting rod side clearance.

Clutch pedal free play is typically 10-25 mm at the pedal; no free play lets the release bearing ride the pressure plate and slip the clutch.

Clutch slip is diagnosed by engine speed rising without vehicle speed under load; judder points to oil contamination, warped flywheel or worn mounts.

Manual gearbox ratios multiply torque: overall ratio = gear ratio x final drive ratio; a lower numerical ratio gives higher top speed, a higher numerical ratio gives better gradeability.

Synchronisers equalise shaft speeds before engagement; grinding on downshift with cold oil indicates worn baulk rings or incorrect oil grade.

Differential allows outer and inner wheels to turn at different speeds in a turn; final drive ratio = ring gear teeth / pinion teeth.

Hypoid differentials need GL-5 oil with the specified limited-slip additive where applicable; wrong oil causes chatter and accelerated wear.

Automatic transmission fluid level is checked at operating temperature with the engine running and the selector in the specified position; overfill causes aeration and foaming.

CV joint clicking on full lock indicates a worn outer joint; a torn boot means grease loss and dirt entry, so the boot is replaced with the joint inspected.

Hydraulic pressure = force / area; a larger master cylinder piston raises pedal effort, and a larger wheel cylinder piston increases braking force.

Brake fluid is hygroscopic; DOT 4 has a higher boiling point than DOT 3, and absorbed moisture causes a spongy pedal and vapour lock when hot.

Air in the hydraulic circuit is removed by bleeding in the maker's sequence, usually farthest wheel from the master cylinder first, keeping the reservoir topped up.

Disc runout, pad thickness and drum ovality are measured with a dial indicator or micrometer; below minimum thickness the part is replaced, not machined further.

Parking brake travel is adjusted at the cable or rear caliper mechanism; dragging brakes show as heat, pull and rapid pad wear.

Wheel alignment: camber is vertical tilt, caster is steering-axis tilt, toe is the difference in front/rear distance of the wheels; incorrect toe causes rapid tyre scrub.

Tyre rotation and correct inflation extend life; underinflation increases sidewall flex and heat, overinflation reduces the contact patch and grip.

MacPherson strut combines spring and damper in one unit; a leaking damper, cupped tyre wear or excessive bounce indicates replacement, and springs are compressed with a proper compressor only.

Ohm's law: V = I x R; power P = V x I. A 12 V circuit drawing 5 A has 2.4 ohm resistance and dissipates 60 W.

Battery capacity is rated in ampere-hours and cold cranking amps; specific gravity of a fully charged lead-acid cell is about 1.265 and drops as it discharges.

Voltage drop testing is done under load: more than about 0.5 V on a cable or connection means excessive resistance, not a faulty component.

Series circuits share current and divide voltage; parallel circuits share voltage and divide current, which is why vehicle loads are wired in parallel.

Alternator output is checked at raised idle with loads on; charging voltage is typically about 13.5-14.5 V, and a diode fault shows as AC ripple.

Starter circuit diagnosis: check battery state of charge, terminal tightness, earth strap and solenoid operation before replacing the starter motor.

Fuses protect circuits and are rated in amperes; a blown fuse is replaced with the same rating, and repeated blowing indicates a short to earth.

Sensors such as MAP, MAF, TPS and oxygen sensors feed the ECU; a scan tool reads live data and fault codes, which are confirmed with wiring and signal tests.

Stoichiometric air-fuel ratio for petrol is about 14.7:1 by mass; rich mixtures raise CO and HC, lean mixtures raise NOx and can misfire.

Diesel combustion is by compression ignition; injection timing too advanced causes knock, too retarded causes smoke and high exhaust temperature.

Three-way catalytic converter controls CO, HC and NOx only near stoichiometric operation, which is why closed-loop oxygen sensor control is used.

PCV recirculates crankcase gases, EGR lowers combustion temperature to cut NOx, and EVAP captures fuel vapour; a loose fuel cap can set an EVAP fault.

Smoke limits: black smoke indicates over-fuelling or restricted air, blue smoke indicates oil burning, white smoke indicates coolant or unburnt fuel.

CNG and LPG kits need a pressure reducer, gas-tight piping, a leak test after installation and periodic cylinder hydro testing per local rules.

Battery electric vehicles have no tailpipe emissions; service safety requires isolating the high-voltage system, using insulated tools and following the maker's lockout procedure.

Fuel injection pressure is far higher on common-rail diesel than on port petrol injection; never crack a high-pressure line with the engine running.

Panel repair order: clean, strip paint, straighten with dolly and hammer, shrink stretched metal, apply body filler thinly, sand, prime, then topcoat.

Paint system layers are pretreatment, primer, base coat and clear coat; each layer needs the specified flash-off time and compatible thinner.

Spray gun distance is typically 15-20 cm with 50% overlap; too close causes runs, too far causes dry overspray and orange peel.

MIG welding uses a consumable wire electrode with shielding gas; current controls penetration, wire speed controls deposition and gas flow protects the weld pool.

Oxy-acetylene welding uses a neutral flame for steel; a carburising flame adds carbon and an oxidising flame burns the metal, and cylinders are stored upright and secured.

Welding safety: remove fuel tanks or purge them, disconnect the battery, use fume extraction, a leather apron and a welding helmet with correct shade.

Panel gaps and shut lines are checked with a gap gauge before and after repair; a misaligned door or bonnet indicates hinge or frame damage.

Trim clips and fasteners are single-use where specified; plastic clips are removed with a trim tool to avoid cracking painted surfaces.

Diagnosis sequence: verify the complaint, gather symptoms, check for obvious causes, read fault codes, test the circuit or system, repair, then confirm the fix by road test.

Fault codes identify a circuit or system, not always the failed part; freeze-frame data and live values narrow the cause before parts are replaced.

Periodic service items: engine oil and filter, air filter, fuel filter, brake inspection, coolant condition, tyre pressure and battery terminals at maker intervals.

OBD-II standardised codes are P (powertrain), B (body), C (chassis) and U (network); a P0300-series code indicates engine misfire detected.

No-start checks in order: battery voltage, cranking speed, fuel pressure, ignition spark, compression, then immobiliser or ECU faults.

Service records and job cards must state complaint, cause, correction, parts used and labour; this protects the customer and the workshop.

Pre-delivery inspection covers fluid levels, tyre pressures, lamp operation, road test and torque check of wheel nuts.

Waste oil, filters and coolant are hazardous waste and go to authorised recyclers; records of disposal are kept.

Communication loop: sender, message, channel, receiver, feedback; a job instruction is confirmed by repeating it back to the supervisor.

Technical vocabulary must be used accurately: clearance, tolerance, torque, backlash and runout are not interchangeable terms.

Workplace documents: job card, inspection report, material requisition, leave application and accident report each follow a fixed format and require signature.

Time management uses priority by urgency and importance; a repair that blocks the vehicle is scheduled before cosmetic work.

Team roles in a workshop are service advisor, technician, parts store keeper and supervisor; escalation follows this chain.

Digital literacy includes reading a scan tool screen, using email for parts ordering and protecting customer data from unauthorised sharing.

Interview and CV basics: state qualification, tools handled and specific repair tasks completed, with measurable examples rather than general claims.

Rights at work include minimum wage, safe workplace, working hours and non-discrimination; grievances are raised through the stated channel.

Costing: total cost = fixed cost + variable cost; profit = revenue - total cost, and break-even units = fixed cost / (price per unit - variable cost per unit).

A quotation separates parts, labour and taxes; labour is charged by standard hours from the maker's time schedule, not by guesswork.

GST-registered invoices must show GSTIN, invoice number, date, description, taxable value, tax rate and amount; records are retained as required by law.

Working capital covers stock, tools and wages before payment arrives; a workshop with slow-paying fleet customers needs a higher buffer.

Customer complaint handling: listen fully, apologise for the inconvenience, confirm the facts, offer a specific remedy and follow up after delivery.

Customer retention depends on clear estimates, on-time delivery, clean vehicle return and an explanation of the work done in plain language.

Warranty terms on parts and labour must be stated in writing before the job starts; hidden charges destroy repeat business.

Small workshop marketing: local listing, referral scheme, service reminders by message and photographs of completed repairs with customer consent.