Auto Service World
Feature   September 1, 2001   by Auto Service World

Fall Test Primer: ASE Parts Specialist Certification

Vechicle Systems Example: Starting and Charging Systems


To help you get started, here is an example of a vehicle system, followed by some ASE-type questions. While this brief example focuses on the Starting and Charging Systems, the ASE Certification Test will cover a variety of systems. The ASE does not include systems information on the test, just questions.

Please note also that the sample questions may not all be answered in this copy. That’s why the ASE requires you to have two years of counter experience before writing a certification test.

While starting and charging systems have become more complex since more and more electronics and electrical systems have populated cars, the basics of the starting and charging system on today’s cars is probably the least changed of the systems located under the hood.

This, of course, in no way detracts from its importance and we should all be thankful that we don’t have to hand crank today’s high compression engines!

The Starting System Circuit is made up of the starter motor and solenoid assembly — whether together or separate, the battery, the starter or ignition switch, and the wiring that connects it all.

The lead-acid Battery is the keystone component of the starting system. It provides the all-important stored electrical energy to start the engine. Each automotive battery is made up of six cells generating 2.1 volts each. Bathed in an acid bath, they are linked in series to provide the customary 12.6 volts. The number of plates in each of these cells helps determine the total amps that the battery can provide at this voltage; the more plates, the more amps. As these become damaged, the ability for the battery to provide its rated CCA diminishes, even though it may still maintain 12.6 volts.

The Starter is an electric motor that provides the rotation to the engine on start-up. As electric current passes through its coil windings, it causes the starter to rotate.

The Starter Drive consists of that drive assembly and the solenoid. There are three basic types: direct drive, solenoid activated; reduction gear solenoid activated; and positive engagement, relay activated.

On the first two, the Solenoid, which usually sits atop the starter, controls the engagement of the pinion gear with the flywheel gear. It also closes the heavy-duty contact that provides the high current to the starter motor. Both occur when the ignition/starter switch is turned to the start position.

The Solenoid is an electromagnetic plunger assembly that, when energized, pulls inward forcing a lever to extend the drive assembly until it meshes with the flywheel. On the reduction gear type, the rotational speed of the starter is stepped down to increase torque for larger engines. A positive engagement, relay actuated system is similar to the direct drive, solenoid activated assembly except that it uses the strong magnetic field generated by the motor’s field coil to pull the plunger lever.

Once started, the Overrunning Clutch allows for the quick disengagement of the pinion gear from the flywheel to prevent damage to the starter from the high engine rotational speeds. A Bendix Drive system is an additional design for this purpose which uses a set of gears on the armature shaft and on the inner surface of the pinion gear. Both systems cause the pinion to be retracted when the engine rotational speed exceeds that of the starter.

Some starter circuits employ a Ballast Resistor bypass circuit. A ballast resistor or resistance wire in series with the ignition coil’s primary circuit is used in older systems to protect it from excessive current but, because the ignition circuit requires full current during starting, either a separate, secondary circuit is employed or a separate set of contacts in the solenoid.

Starting an engine taxes a battery’s abilities. It doesn’t take too many to sap its strength completely. Enter the charging system.

The Charging System has five main components: the alternator, the regulator, the pulley and belt drive system, the fusible link and a dash warning light or gauge.

An Alternator’s job is to generate electricity. This used to fall to a Generator years ago, but an alternator is a more efficient “generator” of electricity. Generators provided DC current to the battery. An Alternator actually produces AC current. Since this is of no use to the battery, a DC electrical device, this current must be converted in to DC current.

The Rectifier or Diode does just that. Diodes only allow electrical current to flow in one direction and prevent the battery from discharging to ground through them and the alternator’s windings. Diodes may be packed singly or combined in a single package. They are mounted on or in the alternator. As alternator rotational speed rises, its rapidly cycling positive and negative electrical pulses (alternating current) is converted into a near continuous, steady DC current. As the alternator’s rotational speed increases, so does the voltage it generates.

The Regulator controls this voltage, preventing it from rising to the point where it can damage electrical components, including the alternator itself. A Regulator works by turning on and off the voltage applied to the rotor through the brushes and slip rings as it rotates. Restricting this current controls the current flow induced in the stator windings. This on/off switching takes place many times per second. The regulator may be internal to the alternator or mounted externally. A malfunctioning regulator can have all sorts of strange effects on other systems. It is not unknown, for instance, for a regulator on a VW to fail and cause the oil pressure light to glow!

The Fusible Link is a safety device designed to protect the voltage regulator, diodes and alternator from short circuits.

Gauges and Lights keep the driver informed, to some extent, of the functioning of the charging system. An ALT warning light will let the driver know of an alternator malfunction, an Ammeter will read the amount of amperes being received by the battery and a voltage gauge will register the voltage being generated by the alternator.

One of the classic problems which occurs with the starting and charging system is the “battery or alternator” question. While alternators may appear to be operating well under some test conditions, they may become erratic after extended driving in hot conditions, for example. Additionally, if the belt tension on the pulley is insufficient, poor charging may result. For counterpeople, it is important to remember that the alternator is not a battery charger. Installing a new one without ensuring that the battery is in good working order is just asking for trouble.

ASE PARTS SPECIALIST TEST SAMPLE QUESTIONS

Here are some questions in the “ASE style,” though supplied by them, so don’t memorize them because they won’t be on the test. You’ll notice that sometimes more than one answer could be correct. In such cases, you should pick the answer that is most likely the right one.

Question 1

All of the following are part of the charging system EXCEPT:

A) alternator

B) fusible link

C) battery

D) regulator

Question 2

Counterperson A says that a battery with a reading of 12.6 volts should be okay for use. Counterperson B says that an alternator should be charging at about 14 volts to keep a battery charged. Who is correct?

A) Counterperson A only

B) Counterperson B only

C) Both Counterperson A and B

D) Neither Counterperson A nor B

Question 3

Parts Specialist A says that the diodes on an alternator convert the AC current to DC current. Parts Specialist B says that the rectifier converts AC current to DC current. Who is correct?

A) Counterperson A only

B) Counterperson B only

C) Both Counterperson A and B

D) Neither Counterperson A nor B

Question 4

Parts Specialist A takes a call from a technician. He says the alternator he just installed on a Honda has an output of only 10 amps when he checked it just after he started the car. You should:

A) Tell him the unit is defective and to send it back.

B) Tell him they all do that.

C) T
ell him to measure the current once the engine has been running for a while.

D) Tell him to check that the alternator belt isn’t slipping.

Question 5

A fusible link is installed to:

A) Protect the electrical system from damaging current.

B) Control the amount of current flowing from the alternator.

C) Protect the alternator from short circuits.

D) Protect the ECU from short circuits.

Question 6

A customer has just returned an alternator for a warranty claim. You should do all of the following EXCEPT:

A) Inspect the alternator for damage.

B) Ensure the Warranty Tag is filled out properly.

C) Send out a replacement unit.

D) Credit the customer’s account for the cost of the claim.

Question 7

On the above diagram, which would be the four o’clock position?

A) X

B) Y

C) W

D) Z

Question 8

Sometimes it is suggested that a technician install a relay in a starter circuit. Why?

A) To protect the starter motor from high current.

B) To ensure that the starter motor does not continue running.

C) To increase the current applied to the starter motor.

D) To sell more relays.

Question 9

A customer walks into the store with an alternator in hand, and asks for a replacement, which you have in stock. Which of the following should you NOT do?

A) Sell him a replacement alternator.

B) Add a core charge to his bill.

C) Advise him to ensure the battery is charged.

D) Try to sell him a new battery.

Question 10

A customer calls with a no-crank problem on a Ford. He has already replaced the battery and the starter was replaced previously, but the problem remains. He says the alternator seems to be working fine. What could be the problem?

A) A non-functioning rectifier.

B) A blown main fuse.

C) Corroded battery cables.

D) A non-functioning starter.

W

Y

SEE AUTOSERVICEWORLD.COM TECH CHATROOM FOR ANSWERS


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