ASE A6 flashcards

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

Voltage Drop Test

A measurement of the voltage lost across a conductor, connection, or switch while current flows; the meter connects in parallel with the part being tested with the circuit energized.

Ohm's Law

The relationship E = I x R, where E is volts, I is amperes, and R is ohms; power equals I x E. Used to predict current flow or resistance in a circuit.

Parasitic Draw

Current that flows with the ignition off and all accessories off after the modules have gone to sleep; the usual acceptable value is 20-50 milliamps.

Relay Terminal Identification

Terminals 85 and 86 connect the relay coil, 30 is the battery feed, 87 is the normally open contact to the load, and 87a is the normally closed contact.

Parallel Circuit Rules

A circuit with multiple current paths: the same voltage appears across each branch, branch currents add to total current, and total resistance is lower than the smallest branch resistance.

12.6 Volts at Rest

Open-circuit voltage of a fully charged 12-volt battery measured after surface charge is removed; it equates to roughly 2.1 volts per cell across six cells.

Battery Load Test

Apply half the rated cold cranking amps for 15 seconds at 21 degrees C; the battery must stay at or above 9.6 volts to pass the test.

Three-Minute Charge Test

Charge a battery at 30-40 amps for three minutes; a voltage above 15.5 volts shows high internal resistance or sulfation and the battery needs replacement.

Specific Gravity Reading

Electrolyte density corrected for temperature; about 1.265 is fully charged, 1.225 is 50 percent, and 1.120 is discharged on a flooded battery.

AGM Charging Difference

Absorbent glass mat batteries use a lower absorption voltage than flooded batteries and must not be equalized; the charger mode must match the battery chemistry installed.

Cranking Voltage Specification

Battery terminal voltage during cranking must stay at or above 9.6 volts at 20 degrees C; a lower reading indicates a weak battery, high cable resistance, or excessive starter draw.

Starter Current Draw

A typical starter draws 150-250 amps while cranking; much higher current points to a seized engine, a shorted starter, or high resistance in the cables.

Neutral Safety Switch

A switch that permits cranking only in Park or Neutral on automatic-transmission vehicles; a misadjusted or failed switch causes a no-crank with otherwise normal electrical operation.

Starter Solenoid Terminals

B connects to battery positive, S receives the start signal from the ignition switch, and M feeds the starter motor; jumping B to S cranks the engine.

Starter Ground Voltage Drop

Measured from the starter case to battery negative during cranking, it should be 0.2-0.3 volt or less; higher readings indicate a bad engine ground strap or cable.

Charging Voltage Specification

At 2000 rpm with accessories off an alternator should produce about 13.5-14.8 volts; below 13.2 volts suggests undercharging and above 15.5 volts suggests overcharging.

Diode Ripple Test

With the engine running, a DMM set to AC volts across the battery should read less than about 0.5 volt; higher AC voltage indicates a failed rectifier diode.

Voltage Sense Circuit

The wire that feeds actual battery voltage back to the voltage regulator; if it is open, the regulator senses low voltage and overcharges the battery.

Alternator Output at Idle

Most alternators produce only 60-70 percent of rated output at idle, so full output testing must be done at the specified engine speed with a carbon pile.

Alternator Diode Leak

A shorted rectifier diode can drain the battery with the key off; disconnect the alternator B+ wire and recheck the parasitic draw to isolate it.

Fast Turn Signal Flash

On a thermal flasher a rapid flash rate means one bulb is burned out or has the wrong resistance; LED bulbs require an electronic flasher or load resistors.

HID Ballast Output

The ballast produces roughly 20,000-25,000 volts to strike the arc and then regulates running voltage; never touch the bulb glass or probe the output.

PWM Lamp Control

Body computers dim or control lamps by pulse-width-modulating the ground circuit; a DMM in duty-cycle mode or an incandescent test lamp confirms the driver output.

Shared Ground Lamp Symptom

Several lamps that dim or brighten together usually share a ground with high resistance; measure voltage drop on the ground side while the lamps are on.

CAN Bus Resistance Check

With the battery disconnected, a good bus measures about 60 ohms across DLC pins 6 and 14 because the two 120-ohm terminating resistors are in parallel.

Fuel Gauge Sender Test

Senders are variable resistors; substituting a known resistor value in place of the sender and watching the gauge shows whether the gauge or the sender is faulty.

Cluster Replacement Programming

A new instrument cluster usually needs the VIN, odometer value, and options programmed with a scan tool, sometimes followed by a theft-deterrent or key relearn.

NTC Temperature Sender

A negative-temperature-coefficient sender decreases resistance as temperature rises; an open sender circuit drives the gauge to cold and a shorted one drives it to hot.

Express Window Relearn

After a battery disconnect or motor replacement the body computer loses window position limits; run the window fully open and fully closed holding the switch to restore express operation.

Wiper Park Switch

An internal switch that keeps the wiper motor powered after the control is turned off so the blades return to the bottom of the windshield and stop there.

SRS Ohmmeter Caution

Never connect an ohmmeter or powered test light to airbag circuits because the meter current can deploy the module; disable the system and wait the specified time first.

Body Control Module Loads

The BCM controls relays, lamps, and accessories through internal drivers; an open relay coil or a bad BCM ground can make several unrelated accessories fail at once.