ASE H6 Electrical/Electronic Systems (Transit Bus) flashcards
ASE H6 Electrical/Electronic Systems (Transit Bus) · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Battery open-circuit voltage
- A rested 12 V lead-acid battery reads about 12.6 V at 77°F when fully charged; lower readings indicate decreasing state of charge.
- Series battery connection
- Connecting batteries in series adds their voltages while amp-hour capacity remains that of one battery; two 12 V batteries in series make a 24 V bank.
- Parallel battery connection
- Connecting batteries in parallel keeps voltage the same and adds amp-hour capacity and cranking current; all batteries must be same type and condition.
- Battery capacity test
- Load a 12 V battery to half its cold-cranking-amp rating for 15 seconds; at 70°F it should stay above 9.6 V.
- Starter voltage drop test
- Measure voltage across each cranking cable or connection while the starter turns; more than about 0.5 V indicates excessive resistance in that part of the circuit.
- No-crank diagnosis
- Check battery state of charge, control-circuit power and ground, start interlock, starter relay, and solenoid operation before condemning the starter motor.
- Alternator rectifier
- The rectifier uses diodes to convert three-phase AC stator output into DC; a failed diode can cause ripple, dim lights, and a no-charge condition.
- Voltage regulator function
- The regulator varies alternator field current to hold charging voltage within specification; too high overcharges batteries, too low leaves them discharged.
- Charge excite circuit
- The excite circuit supplies initial current to the alternator field; an open indicator bulb or wire can prevent charging until engine speed rises.
- Alternator ripple test
- With the engine running, measure AC voltage at the battery; excessive ripple indicates failed rectifier diodes or stator faults.
- Remote voltage sense
- A sense wire tells the regulator the actual battery voltage; high resistance in this wire causes the alternator to overcharge the system.
- LED polarity
- Light-emitting-diode lamps conduct current in one direction only; reversed connections prevent illumination, and low current may not trigger a thermal flasher.
- Turn signal fast flash
- A turn signal that flashes faster than normal usually indicates a burned-out lamp or open circuit on that side, reducing the flasher load.
- Brake lamp circuit
- The brake switch supplies power to the brake lamps independently of the turn-signal switch; both circuits share bulbs in many combination lamps.
- Relay coil and contacts
- The coil is a low-current control electromagnet; the contacts switch high load current, so each must be tested separately with a meter.
- Poor ground backfeed
- When a lamp loses its ground, current can travel through other lamp filaments to find ground, causing dim or cross-illuminated lamps.
- Sender resistance gauge
- Most pressure and temperature gauges read a variable-resistance sender; the gauge indication depends on sender resistance plus wiring resistance.
- Gauge pegged test
- Disconnect the sender: if the gauge pegs, the sender wire is shorted to ground; if it stays low, the sender or feed is open.
- Warning lamp prove-out
- At key-on, warning lamps should illuminate briefly; a lamp that never lights indicates a bulb, LED, cluster, or power/ground fault.
- Data bus gauge failure
- Multiple gauges failing together often indicate a data-bus or cluster power/ground fault rather than several independent sender failures.
- Speedometer calibration
- Speedometer and odometer accuracy depend on vehicle speed sensor signal, tire size, and axle ratio; incorrect calibration affects both.
- J1939 CAN termination
- A J1939 network uses two 120-ohm terminating resistors, one at each end; measured unpowered across CAN_H and CAN_L they read about 60 ohms.
- CAN termination fault
- About 120 ohms indicates one terminator is missing or open; an open reading indicates both are missing or the bus wiring is broken.
- J1708 physical layer
- J1708 is a slower two-wire serial network used for older bus communications; J1587 defines the message content carried on it.
- CAN short fault
- A short from CAN_H or CAN_L to battery power or ground can disable communication for many modules and make them appear offline.
- Multiplex output module
- A multiplex output module receives network commands and switches power or ground to loads such as lamps, relays, and motors.
- Module sleep drain
- A module that fails to sleep keeps network activity alive and can drain batteries; check sleep commands and current draw after shutdown.
- Voltage drop test
- With current flowing, place the meter across a cable or connection; the voltage reading shows resistance loss, and excessive drop indicates a bad connection.
- Fuse rating rule
- A fuse is selected to protect the wire and circuit, not the load; never install a larger fuse to stop blowing.
- Parasitic draw test
- Measure current in series with the battery after modules sleep; compare with the manufacturer's maximum to find abnormal drains.
- Short to ground
- A conductor touching ground bypasses the load and usually blows a fuse or trips a breaker; isolate by disconnecting sections.
- Connector drag test
- A mating terminal or gauge checks terminal tension; loose female terminals cause intermittent voltage drops, heat, and communication faults.