Red Seal Automotive cheat sheet

Torque equals force multiplied by distance; 1 N·m = 0.7376 lb·ft and 1 lb·ft = 1.3558 N·m.

Metric property class 8.8 means a nominal tensile strength of 800 MPa and a yield strength of 640 MPa (80% of tensile).

A metric thread designation such as M8×1.25 means an 8 mm nominal diameter and a 1.25 mm distance between thread crests.

A metric micrometer reading equals the barrel value in millimetres plus the thimble division multiplied by 0.01 mm.

Dial indicator total indicated reading (TIR) equals the maximum gauge reading minus the minimum gauge reading.

WHMIS 2015 Safety Data Sheets contain 16 standardized sections, including hazards, composition, first aid, and disposal.

Lockout/tagout requires isolation of all energy sources and verification of zero energy before work begins.

A feeler gauge is a go/no-go check: the specified blade should enter the clearance with light drag, and the next size up should not.

The four-stroke cycle is intake, compression, power, and exhaust; the crankshaft turns twice and the camshaft turns once per cycle.

Displacement = (π ÷ 4) × bore² × stroke × number of cylinders.

Compression ratio = (swept volume + clearance volume) ÷ clearance volume.

Torque-to-yield bolts are tightened to a torque value plus a specified angle and are replaced when they exceed the specified free length.

On an interference engine, a failed timing belt can allow pistons to contact valves and bend them.

A cylinder leakage test above about 20% leakage, or bubbles in the coolant, indicates ring, valve, or head gasket leakage.

A compression test is run with the throttle wide open and all spark plugs removed; the lowest cylinder should be within 10–15% of the highest.

A healthy engine typically produces a steady idle vacuum of about 17–22 inHg at sea level.

Ohm's law: V = I × R; electrical power P = V × I = I² × R.

Series resistances add directly; for parallel branches, 1/R_total = 1/R1 + 1/R2 + …

A resting 12 V lead-acid battery reads about 12.6 V at 100% state of charge and about 12.0 V at roughly 25%.

Charging system output is typically 13.5–14.7 V at about 2000 rpm with accessories off.

Total voltage drop in a loaded circuit should generally be 0.5 V or less, with each connection or cable contributing about 0.1 V or less.

After modules enter sleep mode, parasitic draw is typically below 50 mA (0.05 A).

A high-speed CAN bus with two 120 Ω terminating resistors measures about 60 Ω between CAN high and CAN low.

In a common automotive relay, terminals 85 and 86 are the coil and terminals 30 and 87 are the switched contacts.

Gear ratio = driven gear teeth ÷ driving gear teeth; a numerically higher ratio multiplies torque and reduces output speed.

Overall drive ratio = transmission gear ratio × final drive ratio.

An open differential delivers equal torque to both wheels but allows them to rotate at different speeds.

A limited-slip differential uses clutch packs or gears to send additional torque to the wheel with more traction.

Driveshaft universal-joint yokes at both ends must be in phase, and operating angles at each end should be equal and opposite.

An inner CV plunge joint accommodates changes in driveshaft length; an outer fixed CV joint allows steering movement.

A numerically higher final drive ratio improves acceleration, lowers top speed, and increases engine speed at a given road speed.

Part-time four-wheel drive must not be engaged on dry, high-traction pavement because the transfer case has no centre differential.

Hydraulic pressure P = force ÷ area; increasing master cylinder bore area reduces line pressure for the same pedal force.

DOT 3 and DOT 4 glycol-based fluids are hygroscopic; DOT 5 is silicone-based and must not be mixed with glycol fluid.

Brake fade from overheated pads raises pedal effort, while brake fluid boil produces a spongy or low pedal.

A common minimum brake pad friction material thickness is about 2 mm (3/32 in), or the OEM specification if different.

Rotor minimum thickness is stamped on the rotor; a rotor below that dimension must be replaced, not resurfaced.

Bleeding typically starts at the wheel farthest from the master cylinder and progresses to the nearest, following OEM sequence.

A lit yellow ABS lamp means antilock function is disabled, while conventional hydraulic braking normally remains available.

An electric parking brake requires service mode before retracting the calipers for pad replacement.

Camber is wheel tilt viewed from the front; negative camber tilts the top of the wheel inward toward the vehicle centreline.

Caster is steering-axis tilt viewed from the side; positive caster tilts the top rearward and improves straight-line stability.

Toe is the difference in distance between the front and rear of a tire pair; toe-in means the front edges are closer together.

Thrust angle is the rear axle centreline relative to the vehicle centreline; a nonzero thrust angle causes dog-tracking.

Steering axis inclination (SAI/KPI) is used with camber to diagnose a bent spindle or strut.

Ackermann geometry causes the inner front wheel to turn at a sharper angle than the outer wheel.

A shock absorber controls spring oscillation; a strut is a structural member that also carries vehicle load.

Excessive ball joint axial or radial play beyond the OEM limit requires replacement of the joint or control arm.

The refrigeration cycle order is compressor, condenser, expansion device, and evaporator.

R-134a and R-1234yf are not interchangeable; they use different service fittings and refrigerant-specific lubricants.

Superheat = evaporator outlet temperature − saturation temperature at the same pressure; a TXV regulates superheat.

Subcooling = condenser outlet liquid temperature − saturation temperature; it indicates liquid refrigerant reserve in the condenser.

Typical manifold gauge readings at 20–30 °C ambient are about 25–45 psi low side and 150–250 psi high side.

An orifice tube system uses an accumulator on the low side; a TXV system uses a receiver-drier on the high side.

The system must hold vacuum after evacuation to confirm no air or moisture remains and no leak exists.

A blend door actuator controls air temperature by mixing air passing through the heater core and evaporator.

SRS deployment requires impact sensors and an airbag control module; battery disconnect and OEM wait time precede restraint service.

Seat belt pretensioners deploy with the airbags and are one-time-use components that must be replaced after firing.

High-strength and ultra-high-strength steel require OEM repair procedures because heat from welding can reduce strength.

Panel gap and flush are measured in millimetres; consistent gaps indicate correct panel alignment and fit.

Galvanic corrosion occurs when dissimilar metals contact an electrolyte; the less noble metal becomes anodic and corrodes.

Windshield urethane is a structural adhesive; the vehicle must not be driven until the specified cure time has elapsed.

ADAS cameras and radar units typically require calibration after windshield replacement, suspension work, or alignment.

Body sealer and cavity wax restore corrosion protection at welded and hemmed joints after collision repair.