ASE T6 Electrical/Electronic Systems (Medium/Heavy Truck) flashcards

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

Voltage drop test

Measures voltage difference across a connection or cable while current flows; more than about 0.5 V on a 12 V circuit indicates excessive resistance.

Parasitic draw

Current drawn by the vehicle with all accessories off and modules asleep; measured in series with the negative cable, typically about 50 mA or less.

Series circuit

A circuit with one current path; current is the same through all loads, voltage divides across them, and total resistance is the sum.

Parallel circuit

A circuit with multiple current paths; voltage is equal across branches, current divides, and total resistance is less than the smallest branch.

Short to ground

An unintended path from a circuit to ground that bypasses the load, usually causing high current and a blown fuse or fusible link.

Ohm's law

The relationship E = I × R, where E is voltage in volts, I is current in amperes, and R is resistance in ohms.

Battery state of charge

Approximate open-circuit voltage after rest: about 12.6 V at 100 percent, 12.4 V at 75 percent, 12.2 V at 50 percent, and 12.0 V at 25 percent.

Battery load test

Applies about half the CCA rating for 15 seconds; a good battery holds at least 9.6 V at 70 degrees Fahrenheit.

Parallel battery connection

Connecting batteries positive to positive and negative to negative keeps system voltage the same while adding reserve capacity and cranking current.

Series battery connection

Connecting batteries positive to negative adds the voltage of each battery while capacity and cranking current remain the same as one battery.

Starter solenoid windings

Pull-in and hold-in windings engage the starter drive; a failed winding causes a click without cranking even with a good battery.

Cranking voltage drop

Voltage lost across cables and connections during cranking; more than about 0.5 V per cable or connection indicates excessive resistance.

Neutral start switch

Prevents cranking unless the transmission is in neutral or park; an open switch causes no crank with normal battery voltage.

Alternator output voltage

Charging voltage measured at the battery with the engine running, typically 13.8 to 14.8 V at operating temperature per OEM specification.

AC ripple test

Measures alternating current voltage at the battery with the engine running; excessive ripple indicates failed rectifier diodes in the alternator.

Voltage regulator

Controls alternator field current to hold charging voltage within specification; failure causes overcharging or undercharging.

Full-fielding

Bypassing the voltage regulator to command maximum alternator output for testing; must stay within OEM limits to avoid damage.

Diode trio

Rectifier diodes that convert alternator AC to DC; a failed diode causes low output, AC ripple, or battery drain with the engine off.

Serpentine belt slip

A loose or glazed belt slips under load, causing low charging output, squealing, and glazing that requires belt or tensioner service.

Sealed beam aiming

Headlamp adjustment performed per OEM or DOT procedure so the beam pattern meets specification and does not cause glare.

Fast turn signal flash

A flasher that blinks faster than normal usually indicates a burned-out bulb or incorrect wattage on that side of the circuit.

LED lamp load

LED lamps draw less current than incandescent bulbs, so some flashers and lamp-out monitors need load resistors or a compatible flasher.

Lamp ground fault

Poor ground at a lamp housing increases resistance and causes dim or inoperative lamps; confirm with a voltage drop test.

Brake pedal switch

Controls stop lamp operation; misadjustment causes no brake lights or a battery drain from lamps staying on.

Variable-resistance sender

A sending unit whose resistance changes with temperature, pressure, or fuel level; the gauge interprets the resistance as a reading.

Gauge pegging test

Grounding or opening the sender wire to see if the gauge sweeps isolates whether the sender, wiring, or gauge is faulty.

Data bus gauge failure

When several gauges fail or blank together, suspect a data bus or cluster communication fault rather than individual senders.

Vehicle speed sensor

Provides speed input to the ECM or cluster for the speedometer and odometer; a faulty sensor causes erratic or no speed indication.

Horn relay circuit

The horn button grounds the relay coil, which closes contacts to power the horns; check fuse, relay, button, and grounds.

Wiper park circuit

A switch inside the wiper motor that keeps the motor powered until the blades reach the park position after the switch is turned off.

Wiper linkage binding

Seized pivots or bent linkage cause slow or stalled wipers and can blow the fuse; check linkage freedom before replacing the motor.

Washer pump test

Check the fuse, switch, and connector voltage at the pump; a pump that receives voltage and ground but does not run is defective.