Electrical And Comfort Control Systems Flashcards
Which of the following should be used to perform an IOD (ignition-off-draw) test on a vehicle?
“A. Ohmmeter
B. Ammeter
C. Voltmeter
D. Jumper wire”
“Answer B
An ammeter capable of accurately reading milliamps must be used. The preferred method of performing the test is to use an inductive pick up digital ammeter clamped onto the positive cable close to the battery-positive terminal. An older method would be to use an ammeter placed in series between a separated positive battery terminal post. “
You are performing an IOD test on an automobile equipped with multiple computer systems. The engine has been key-off for 30-minute period and the ammeter reading is 0.045 amps. what should you do next?
“A .Remove all the fuses and retest
B. One by one, remove and replace each fuse and retest
C. Nothing, 0,045 amps battery drain is acceptable
D. Replace the battery “
“Answer C
The ignition-off current draw required by current vehicles with multiple control modules networked to a chassis data bus can be up to 0.60 amps. When performing the IOD test, ensure that the vehicle ignition has been switched off for at least 20 minutes. This will ensure that all of the computers are in ““sleep”” mode “
When the conduit on a 12 V-DC insulated electrical wire wears through and it contacts the vehicle frame, what results is known as:
“A. An open
B. A fire
C. A short to ground
D. A short to voltage”
“Answer C
When the insultation on a 12V-DC wire fails and it contacts the chassis, a short to ground has occurred. A fire should not occur unless the circuit protection device has been bypassed. “
If an electrical accessory was spliced into part of the insulated circuit. which of the following would result in the circuit?
“A. Current increase
B. Current decrease
C. Resistance increases
D. Voltage decreases”
“Answer A
An additional electrical accessory spliced into the insulated circuit provides another path for current flow. Voltage applied to the circuit would remain the same, while total circuit resistance would drop (due to the added path) “
Which of the following is the preferred method of testing the integrity of a series of standard blade-type fuses in an electrical fuse panel?
“A. Pull each fuse, use DVOM ohmmeter to test continuity
B. Pull each fuse, use jumper wires and an ammeter in series
C. Use DVOM in V-DC mode and test each fuse in position at shoulder test points
D. Pull each fuse and observe fusible medium through the plastic”
“Answer C
The preferred method of testing the integrity of a series of standard blade-type fuses in an electrical fuse panel is to use a DVOM in V-DC mode and test each fuse in position at shoulder test points, because this method does not require the removal of the fuse from the circuit. Caution: use the DVOM in V-DC mode and test each fuse in position at shoulder test points with circuits energized! “
Which of the following electrical cable sizes would be an appropriate specification for an automobile battery cable?
“A. AWG #2
B. AWG #6
C. AWG #10
D.AWG #14”
“Answer A
AWG (American wire guage) cable sectional areas increase in size as the number specifications lowers. The electrical cable sizes suitable for automobile battery cables are AWG numbers 0, 1, 2, and 4. Note that AWG sizes descend below zero, as in 00,000 and 0000, with the last having the highest sectional area and therefore having the highest current-carrying capability “
What color is used for the high-voltage wiring insulation in high-potential hybrid vehicle electrical circuits?
“A. Red
B. Orange
C. White
D. Blue”
“Answer B
The color used for the high-voltage wiring insulation in high-potential hybrid vehicle electrical circuits (144V, 275V, 432V) is orange: extreme caution should be exercised when working around high-potential circuits. “
The electric horn on a vehicle does not sound. Where should you begin to troubleshoot the malfunction?
“A. At the horn
B. At horn circuit fuse
C. At the horn button/switch
D. At the horn relay “
“Answer D
As a rule in electrical circuit troubleshooting, it makes sense to begin by checking out the relay. The relay is usually easy to access and will provide an immediate indication of weather the problem is in the control or power circuit of the malfunctioning component “
When a battery has to be disconnected from a vehicle, which of the following is the appropriate method for ensuring that no memory loss occurs in any of the vehicle computers networked to the data bus?
“A. Quickly install a backup battery after disconnecting the original
B. Install a 9V-DC battery anywhere in the circuit
C. Plug a 12V-DC memory saver into a power outlet/ lighter socket
D. Use booster cables from another vehicle to maintain chassis voltage”
"Answer C When a battery has to be disconnected from a vehicle, a 12V-DC memory saver should be plugged into a power outlet/ lighter socket to ensure no memory loss occurs to any of the vehicle computers networked to the data bus. This is simply good customer service. The consequences of not protecting on-board memory will require the rewriting of power control module running strategies (may take up to 80km of operation) and resetting of radio presets. "
The high-voltage battery pack has become discharged on a hybrid-drive vehicle. What should be done to crank and start the engine?
“A. The vehicle must be push-started
B. Boost from another vehicle with high-voltage hybrid drive
C. The high-voltage battery pack must be slow-charged
D. Boost using another 12V-DC source to crank the secondary starter “
“Answer D
When the high-voltage battery pack becomes discharged on a hybrid-drive vehicle, the primary (high-voltage) starter will not crank the engine. however, most hybrid vehicles are equipped with a secondary 12V-DC starter motor to cover this situation. Never attempt any type of high-voltage boost under these circumstances–it can be dangerous”
Rotor resistance is being tested on an alternator by attaching DVOM leads to the A and F terminal screws. Which of the following must be done before performing the test?
“A. Run engine at 1500 rpm
B. Remove alternator from the engine
C. Disconnect the battery
D. Remove the alternator drive belt”
“Answer C
This is a standard test on one type of commonly used alternator. A DVOM is used in ohmmeter mode and although it can be performed in-vehicle, the battery must be disconnected before the test is performed.
“
A customer complains that the DRL (daylight running lights) on his vehicle switch off when the engine is on and the parking brake actuated. which of the following is the likely cause
“A. Short between the DRL and parking brake circuit
B. Poor ground at DRL lamp socket
C. Intermittent open in the DRL circuit
D. Normal condition in some vehicles “
“Answer D
The DRL on some manufactures; vehicle are designed to switch off when the parking brake is actuated’ this acts as a power saver when the vehicle is being serviced “
The turn signals on a vehicle equipped with dual filament tail-light bulbs flash rapidly when a right turn is signaled. Which of the following would be the more likely cause of this condition?
“A. An open in the right-turn signal circuit
B. A dead short to ground in the right-turn circuit
C. Feedback connection at the bulb circuit between the turn and tail light terminals
D. A failed tail light filament in the right side dual filament bulb”
“Answer C
A feedback connection at the bulb circuit between the turn and tail-light terminals could cause this condition. The increased flashing is a result of higher current load through the flasher circuit. “
Which of the electrical devices supplies an input signal to the cruise-control electronics?
“A. Instrument cluster unit
B. Stoplight switch
C. Tail light bulb
D. Turn light switch”
“Answer B
The stoplight switch usually supplies an input signal to the cruise-control electronics that is used to interrupt set speed programming “
Which of the following would be the more likely cause of an HID headlamp failure?
“A. Failed bulb filament
B. Corroded bulb socket
C. Failed HID control module
D. Burned out electrodes”
“Answer D
HID light units are illuminated by electrical discharge fired between two electrodes encased in a xenon gas-filled tube. A very high-potential arc is created to ignite the arc, after which a potential of around 80 volts is required to maintain it. Used properly, HID lights last much longer than any current type of incandescent light : the main cause of failure is burned electrodes resulting from frequent short on/off cycles or headlight flashing. “
Source voltage on an automobile with its engine running and headlights switched o, is measured at 13.5V. If the voltage available at the positive terminal on one of the headlights is measured at 12.7V, which of the following is correct ?
“A. The charging circuit is defective
B. The headlight circuit is functioning properly
C. The headlight being tested is not properly grounded
D. There is excessive resistance in the insulated side of the headlight circuit “
“Answer D
A voltage loses of 0.8 V on the insulated side of the headlight is unacceptable. Make sure you know how to perform voltage-drop testing on some of the typical specifications you might expect to see “
A headlight circuit uses a virtual, cycling circuit breaker. How does this differ from a headlamp circuit that uses a mechanical circuit breaker?
“A. Virtual circuit breakers must be backup-protected by a fuse
B. Virtual circuit breakers can only handle low-current loads
C. Virtual circuit breakers are more sensitive to voltage dump
D. Virtual circuit breakers have no moving parts”
“Answer D
Virtual circuit breakers are becoming more commonly used, and they differ from mechanical circuit breakers in that there are no moving parts: they are solid state and cycle on and off, controlled by microprocessor signal. “
On a standard SAE-coded relay, what is the common terminal coded as?
“A. 1
B. 3
C. 3
D. 5”
“Answer B
The common terminal is coded #3 (this was coded #30 using the older terminal allocations). Make sure you can correlate the new and older terminal assignments; this can be invaluable in troubleshooting”
1= coil = 85 2= coil = 86 3=common connection to NC and NO terminals =30 4=NC (normally closed) = 87a 5= NO (normally open) = 87
How many wires are used in the multiplexing backbone used by a CAN 2.0 data bus (J1850), not counting the shield?
“A. 16
B. 8
C. 2
D. 1”
“Answer C
Two wires are used in the multiplexing backbone used by a CAN 2.0 data bus (J1850) : specifically this is a twisted wire pair that may or may not be shielded. This forms the data backbone of a vehicle multiplex communications system. “
When troubleshooting a complaint of insufficient passenger compartment heat during cold weather operation, which of the following possible causes should you check first?
“A. Temperature of upper radiator hose
B. Engine thermostat
C. Heater core restriction
D. Heater control valve operation”
“Answer A
When troubleshooting any complaint, eliminate the easy potential causes of the problem first. In the case of insufficient passenger compartment heat during cold weather operation, you should check the temperature of the upper radiator hose when the engine appears to be at operating temperature first. That requires the least amount of time and will indicate how the coolant is being circulated in the system and the role played by the thermostat”
Which of the following would be the more costly consequence of using a mineral-based oil in an HFC-134a A/C system? “A. Reduced system performance
B. Contaminated refrigerant
C. Compressor failure due to insufficient lubrication
D. Passenger compartment odor”
“Answer C
The more costly consequence of using mineral base oil in an HFC-134a A/C system would be its potential to cause a compressor failure due to lack of lubrication. HFC-134a systems must use PAG or esther based refrigerant. Using the mineral base oil in an HFC-134a system will contaminate the refrigerant and may also cause system underperformance, but neither will be as costly as a compressor replacement “
What is the appropriate tool for electrically assessing the circuit for the field coils of an A/C compressor clutch?
“A. Voltmeter
B. Ammeter
C. Diode tester
D. Ohmmeter”
“Answer A
The circuit for the field coils of an A/C compressor clutch should be tested for voltage using a voltmeter: when activated, there should be battery or system voltage present”
Under which of the following service procedures would it be acceptable to have both the high and low side hand valves open at the same time?
“A. Evacuating the A/C system
B. Recharging with the A/C system running
C. Checking for leaks with the A/C system running
D. System performance testing with the A/C running”
“Answer A
The only time that both the high- and low- side hand valves on an A/C system should be open at the same time is during evacuation or reclaiming refrigerant with the system not running. “
What would result if an HFC-134a A/C system were 25% overcharged with refrigerant during service?
“A. Passenger compartment temperatures would be cooler than specified
B. The A/C system would operate for 25% longer before next service
C. Ester oil becomes permanently contaminated
D. The A/C system would operate at lower efficiency “
“Answer D
If an HFC-134a A/C system were to be 25% overcharged with refrigerant during servicing it would operate at lower efficiency than specified. Always use the specified weight of refrigerant”
What should prevent refrigerant discharge to atmosphere in the event of a high-pressure service valve leak in an HFC-134a system?
“A. Depressor pin
B. O-ring in the service valve cap
C. Check engine alert to driver
D. None, the refrigerant completely discharges to atmosphere”
“Answer B
The failsafe device used in an HFC-134a AC system in the event of a high-pressure service valve leak is an O-ring located in the service valve cap. You should check the integrity of this O-ring each time the AC system is serviced. “
After performing a hydrometer test on a fully charged battery, cell 1 has a specific gravity of 1.279 and cell 2 has specific gravity of 1.225. What should be done to the battery?
“A. Recharge and test
B. Return to service
C. Replace
D. Replace electrolyte”
“Answer C
Because the variation between the specific gravity in the two cells is greater than 0.050 on a fully charged battery, the battery needs to be replaced “
Which of the following would cause a starter motor to whine while engaged?
“A. Defective solenoid
B. Worn nose cone roller-bearing set
C. Defective flywheel ring gear
D. Worn starter brushes”
“Answer C
A defective or marred flywheel will cause an imperfect fit between the starter pinon gear and the flywheel ring gear teeth. The result of this irregular gear mesh can be a whine while the gears are in mesh. “
When replacing a starter that can be shimmed, what is the necessary clearance between the flywheel and the starter pinion?
“A. 1/16”” (1.59mm)
B. 1/8”” (3.18mm)
C. 3/16”” (4.76mm)
D. 1/4”” (6.35mm)”
“Answer B
On a shimable starter, the clearance between the flywheel and the starter drive shaft is specified at 1/8”” (3.18 mm)”
When cranking an engine, the starter motor turns over slowly. which of the following is a probable cause?
“A. Neutral safety switch
B. Worn starter bushings
C. Low restance in the negative cable
D. Excessive battery CCA”
“Answer B
Worn starter bushings can cause the starter armature to dig into the pole shoes and bind. If the bushings are worn severely, the starter may fail to turn over”
A started motor will not crank and the headlamps dim when the starting circuit is energized. The batter test is acceptable and the connections are corrosion-free. Which of the following should be checked next?
“A. Positive battery cable for an open circuit
B. Neutral safety switch for high resistance
C. Ignition switch for high resistance
D. Started mounting for flange corrosion”
“Answer D
If the starter has corrosion or high resistance in the ground circuit (that is, the mounting flange between the starter and the transmission or engine), there will be voltage drop through ground. This voltage drop can result in a no-crank condition”
