4290-153 revision

4290-153 revision Pt1

​There are two types of current:- Alternating current (AC) and Direct current (DC).

​Motors turn electrical energy into mechanical energy.

By moving magnets past a conductor we can create electrical currents this is in principle a generator.

Generators turn mechanical energy into electrical energy.

As electric current flows, some of this energy can be turned into heat – lighting and screen demist.

​There are four main units of electricity that we will be using:

Volts - V

Amps - I

Ohms - R

Watts – W.

​Voltage is described in two ways the amount of stored pressure, when everything is switched off. Also the pressure in system when a circuit is switched on.

Stored electrical pressure is known as electromotive force (EMF).

When circuit is switched on it is called potential difference (Pd).

Looking at gauge on previous slide with tap off the pressure is high (EMF) open the tap and pressure will drop slightly – potential difference.

​Amps are used to measure the current flow in part of a circuit. The quantity of stored electricity is shown as amp hours (Ah). E.G. a 100Ah battery contains enough electricity to:

Provide 100amps for 1 hour.

1 amp for 100 hours

10 amps for 10 hours, ETC.  Any sum multiplied to make 100. (4 x 25, 5 x 20).

​

​Ohm. Resistance to electrical flow is measured in ohms. To put this in electrical terms: Large diameter wire, low resistance – electricity flows easily.

Small diameter wire, high resistance – electricity does not flow as easily.

Short wire, low resistance.

Long wire, high resistance.

​Watt. The measurement of electrical power is watts.

​

​

As we measure power usage in watts, you will need to understand how we can work out what the power required is, or what power you are getting through a circuit.

This is important when you need to know the amount of circuit protection you require. Or if you are going to upgrade some electrical components.

​We can find the power consumption by doing this: Power (W) = Voltage (V) x Current (A)

12 volts x 3 amps = 36 watts

Multiple Choice

A colleague suffers an electric shock when using an electric drill. Your first action is:

• pull the drill 

  away from them

• ring the 

  emergency 

  services

• inform your 

  supervisor

• switch off the 

  power supply

Multiple Choice

The unit of electrical power is the:

• Watt

• Amp

• Volt

• Ohm

Multiple Choice

A repair on a customer's vehicle is held up because you are awaiting parts to be delivered. You should:

• make yourself 

  busy by cleaning

   up your work area

• finish any aspects you can until the

   parts arrive

• immediately inform your supervisor of the problem

• stop working on the vehicle and wait 

  for the parts

Multiple Choice

A lamp with a poor earth connection will cause:

• the lamp to be 

  brighter

• the bulb to blow

• the circuit fuse to blow

• the lamp to be dim

Multiple Choice

What is the maximum reading the meter can display with the switch in the selected position?

• 10 amps

• 20 volts AC

• 20 volts DC

• 12 volts DC

​Q1. If a person receives an electric shock, you should isolate power - do not touch them until power source removed. Health & Safety.

​Q2. Power (work) is measured in Watts. Pressure Volts, Ease of flow Ohm, Amount of flow Amp.

​Q3. If there are any delays in repair, you may 'Breach' contract, you must contact customer and amend contract. Record whom you spoke to when you spoke, and agreed change to contract. Your supervisor will, make call.

​Q4. If the circuit has a poor earth the resistance will increase, this will reduce the current flowing, making lamp dim.

​Q5. The meter is set in VDC on the 20. so maximum it will read is 20 VDC, this would be choice when working on a 12v system.

​There are two circuit types used in car wiring. These are Series and Parallel.

​It important to understand how each operates. Some circuits (car lighting) may use parallel across the car and be in series front to rear. This is to keep at least one side illuminated if short, and fuse blows.

When testing circuits using Ohm’s Law they behave differently.

​Series current runs through first lamp, into second lamp. This reduces voltage at second lamp, so it will not be as bright.

​Parallel current runs to both lamps. Equal amount of current to each lamp.

​Modern cars have negative earth, this means that the negative battery terminal connects directly to the vehicle body. The consumers are ‘switched’ by opening and closing the positive feed.

​When disconnecting the battery always remove the Negative first.

​When fitting a battery connect the Live first.

​Earth – ground, chassis.

Switched – Supply feed open & close.

erminal – Battery connections.

Live – Larger of terminals.

Negative – smaller terminal.

​Convention states that electricity flows from positive to negative. In fact electrons flow, Negative to Positive. However for the ease of use. All reference will follow conventional flow, unless specifically stated as “Electron Flow”.

​Relays

A relay is a remote switch, which allows a small voltage to turn on a larger voltage supply. Wiring (DIN) for a standard Relay N.O.

​30 – Battery positive.

87 – Live output

85 – Battery to Ground (Earth).

86 – Trigger signal in

Circuit protection is provided by fuses. This is designed to blow (burn out) at just above the amperage rating for the circuit, but still below amperage that could cause wiring to overheat or consumer unit to burn out.

Fuses can be blown by excess power through wiring, a direct short to earth or by poor connections, causing heat.

You must never substitute a blown fuse for one with larger rating.​

​Each type of fuse is marked with a current rating

​In a 1990’s car there is around 1.5 Km’s of wiring, Today it is less? This is because today we use CANbus systems where two wires can control several different consumers. The Controller Area Network (CAN bus) is the nervous system, enabling communication. In turn, 'nodes' or 'electronic control units' (ECUs) are like parts of the body, interconnected via the CAN bus. Information sensed by one part can be shared with another.

CAN bus has two outputs. Hi & Lo.

Hi – 2.5 v up

Lo – 2.5 v down

These mirror each other and one is back up to the other​

​Cables. To aid with finding which wire runs to a consumer, the outer insulating is colour coded.

Usually on a DIN wiring diagram the initials will be for the GERMAN word for the colour.

SW = Black (Schwarz)

WS = White (Weisse)

G = Yellow (Gelb)

​The thicker the cable the more easily the current can flow through it.

Battery cables are very thick to allow large amount of flow.

​Inside if the insulator the copper wire is made up from numbers of strands of copper wire, also these individual strands can be different thickness.

​So what is an ECU (Electronic Control Module)? Quite simply put ECU is a device that controls all the electronic features in a car. This may range from fuel injection to maintaining perfect cabin temperature to controlling braking and suspension. Some vehicles have multiple ECU controlling different features while some have a single one controlling everything.

​An Electronic control module, uses information from sensors, which it then determines what actuators to operate, based on this information. An ECU gives ability to ‘Self-Diagnose’.

​The engine management of a car is controlled by a ECU. This module has sensors informing it of:

​Types of sensor

Position Sensors

Pressure Sensors

Temperature Sensors

The engine management once it has processed the incoming data, signals the actuators, to do something.

​Types of actuator

Injector

Relay

Motor

Switch

Solenoid.

​

​Items arrowed toward ECU are

Sensors.

Items arrowed from ECU are actuators

​

​Inductive and Hall Effect RPM sensors in today’s vehicles, mainly are used for measuring the rpm and determining the position of crankshaft or camshaft at engine management systems, as well as measuring the speed (rpm) of the wheels at ABS systems, ESP systems, etc.

​Inductive – AC two wire. These give a Sine wave, alternating current, Analog.

Hall – DC three wire. Square wave, Direct current, Digital.

Multiple Choice

What type of actuator is used on a remotely switched fuel flap release?

• A motor and gear actuator

• A pneumatic motor

• A stepper motor

• An electric solenoid

Multiple Choice

What device is used to control the duration of the heater systems operation?

• A regulator and a relay

• A relay and timer

• A thermistor and relay

• A relay and resistor

Multiple Choice

What electrical unit is used to control the power flow in the circuit?

• A regulator

• A diode

• A relay

• A thyristor

Multiple Choice

When testing a suspected faulty door actuator, what would you expect to find on the two activation wires when the central locking is active?

• Both showing an earth

• Both reading 12 volt

• 12 volts and an earth

• 0 Ohms

Multiple Choice

In modern, heavy commercial vehicles what is the most common use for LED lighting?

• Side marker lights

• Headlight low beam

• Front driving lights

• Front fog lights

​Q1. A solenoid is used to release flap, it then is pushed open by a spring. Pneumatic systems use air to operate a solenoid valve.

​Q2. To allow high power flow remotely a relay is used, to switch off power a timer is used - this is usually incorporated within the relay, known as a Timer Relay.

​Q3. To remotely control power a relay is used, where a small power can operate coil, to connect high power circuit.

​Q4. For an electrical actuator to operate it will require a (12v) feed and an earth (common ground), this is a circuit.

​Q5. The side marker lights on an HGV are often on 24/7, LED's use less power than conventional incandescent lamps.