PLC Resource Cover Sheet
Electric Cooling Fan Circuit
Program Area(s):
X
Autobody / Collision Repair
Commercial Art
Electrical
Automotive Technology
Cosmetology
Health / Medical
Carpentry
Culinary
Welding
Other (please specify):
Task/Competencies and/or Academic Skills Addressed in Lesson/Resource(s):
Electric Cooling Fan Circuit
Grade Level(s):
10-12
Related Academic Standards:
Commonwealth of Pennsylvania Standards and Anchors
STANDARDS:
2.1.11.D – Use exponential, scientific, and calculator notation to represent any rational number.
1.1.11. A – Apply appropriate strategies to analyze, interpret, and evaluate author’s use of techniques and
elements of fiction and non-fiction for rhetorical and aesthetic purpose.
3.2.10. B1 – Analyze the relationships among the net forces acting on a body, the mass of the body, and the
resulting acceleration using Newton’s Second Law of motion.
ANCHORS:
M11.A.2.1 – Apply ratio and/or proportion in problem-solving situations.
R11.A.2.5 – Summarize a nonfictional text as a whole.
S11.C.3 – Principles of motion and energy.
ELIGIBLE CONTENT:
M.11.A.2.1.1 – Solve problems using operations with rational numbers including rates and percents (single and
multi-step and multiple procedure operations) (e.g., distance, work and mixture problems, etc.).
R.11.A.2.5.1 – Summarize the major points, processes and/or events of a nonfictional text as a whole.
S11.C.3.1.4 – Explain how electricity produces magnetism and how magnetism produces electricity as two
aspects of a single electromagnetic force.
BIG IDEAS: The automotive electrical system is a key component to all vehicles manufactured today.
CONCEPTS:
Electro magnetism uses low amperage to control high amperage.
A fuse size needs to cover the draw of the circuit.
The cooling fan circuit is protected by the fuse from excessive current flow.
COMPETENCIES:
Use wiring diagrams during diagnosis of electrical circuit problems.
Check electrical circuit with a test light.
Inspect and test switches, connectors, relays, solid state devices and wires of electrical/electronic circuits;
perform necessary action.
Vocabulary:
Battery – A device containing one or more cells that produce electricity through electrochemical action.
Fan motor – A small “dc” (direct current) motor, mounted on a bracket and secured to the radiator.
Relay – A magnetically operated switch used to make or break current flow in a circuit.
Thermostatic switch – (also known as thermal switch) Electrical component that shuts off an air conditioning
compressor when the evaporator temperature approaches the freezing point.
Fuses – Device that interrupts the current if a circuit is overloaded or a short occurs.
Objectives:
Students will build the electric cooling fan circuit with the components provided with 100% accuracy based on the
performance checklist.
Essential Question(s):
Describe how a cooling fan circuit works and determine if there is a difference between computerized vehicles
and non-computerized vehicles.
Duration:
2 hours
Materials:
Test light, Battery, Fan motor, Relay, Fuses, Thermal switch, Circuitry, Wire diagrams, heat gun
Turning Point System or other clicker or quick response system
Suggested Instructional Strategies:
Higher Order thinking: Analyze
Select all that apply: Double-click over the box and select “Checked” to select the strategy.
Active engagement
Auditory
Differentiated Learning
Explicit Instruction
Inquiry Based
Kinesthetic/Tactile
Metacognition
Modeling
Musical/Rythmic
Nonlinguistic Representation
Project Based Learning
Scaffolding
Simulation
Verbal/Linguistic
Visual/Spacial
Webb’s Depth of Knowledge: Extended Thinking
Webb’s Depth of Knowledge: Recall
Webb’s Depth of Knowledge: Skill/Concept
Webb’s Depth of Knowledge: Strategic Thinking
W = Students develop an understanding of the importance of being able to troubleshoot a vehicle that is
having overheating problems. They realize that an understanding of the electrical system is essential to
their success as a technician. It starts with determining prior knowledge by using the admit slips and their
ideas for the electro-magnet and the components. The assessment continues throughout the lesson and
ends with using the Turning Point Active Engagement System to check for understanding of the big
concepts. The students will also complete a ticket out the door slip at the end of the lesson to determine
if there are any gaps in their understanding and if any concepts need to be re-taught.
H = The teacher holds up a wire, D cell battery and nail, and asks students what they could create with
these three things?
E = The students work with real components to build the circuit, then they progress to troubleshooting
problems on vehicles that were “bugged,” and also discussing client scenarios that simulate the “real
world” situations.
R = When the students build their circuit, troubleshoot a vehicle or answer a scenario, they will reflect on
the process and may need to rethink a solution.
E = The students will have immediate feedback when the circuit they build works or doesn’t work. That
will be their self evaluation.
T = The teacher offers one-on one help to any student that needs it to build the circuit on paper, before
they build it with the components. Teams will be grouped to include varying ability levels to allow for peer
mentoring.
O = Teacher will model the activities, then direct students to continue with the team activities. All of the
activities build on the student’s knowledge and skills, to eventually troubleshoot a vehicle alone or on a
team, as well as determine answers to the real life scenarios.
Instructional Procedures:
Getting Started: When the students arrive they get an admit slip and need to answer the following
questions: What do you know about fuses? How are they used by a vehicle? What do you know about
batteries? How and where are they used by a vehicle? Have we studied anything else that had a fuse or
a battery?
Engage: The teacher models with a wire, battery and a nail. “Have you used these three things to make
something? What could it create?” “Yes, an electro-magnet.’ This is a key component in the electric
cooling fan circuit. Let’s take a look at the components in the cooling fan circuit and see if we can figure
out how they work together.
Components of a cooling fan circuit
Explore: Students come up to the front of the room and examine the components and try to decide how it
works. What is each part’s function?
Explain: Students will be given a graphic organizer to categorize each component and their function.
 Battery – This is the power source for the circuit. Normal OCV or open circuit voltage is 12.6 volts.
Current flow will be from positive to negative in the system.
 Fuses – These will protect the circuit from any excessive current flow. If a positive wire were to come
in contact with a negative wire, the current will flow too fast being there is no resistance in the circuit.
The excessive flow of electrons will travel so fast that the friction generated as it flows through the
fuse will heat the element in the fuse to the point that it will burn out opening the circuit and protecting
the circuit and its components.
 Numeracy – Fuses are rated in amps. There is a formula for calculating circuit protection. Because of
a voltage spike when a component is turned on, a component that draws 20 amps will draw slightly
above that when first energized. To accommodate for this excessive initial draw in amperage you
would multiply the amp draw of the component by 30% and adding that to the amp draw of the
component to come up with the total amp draw and/or circuit protection needed.
PRACTICE TOGETHER:
Example – Component draw is 20 amps.
Formula – 20 X 30% = 6 20 + 6 = 26 A 30 amp fuse would be needed to protect this circuit.
Fuses come in 2,5,10,15,20,25,30,40,50,60,80,100,120 and 140 amp sizes. If your calculations called for
an amp rating that is in between two of these available fuses, you would go to the next largest size.
See attached Numeracy worksheet. Practice in group “NOW”. Let’s try another example with your
group:
Example:
A brake light circuit uses 4 bulbs each with an amp draw of 1.5 amps. The total brake lamp circuit draws 6
amps (1.5 amps x 4 bulbs).
6 amps x 30% =1.8
Add 1.8 to the 6 amps to find the total amps in the circuit 7.8 amps.
Fuses come in 2,5,10,15,20,25,30,40,50,60,80,100,120 and 140 amp sizes. Select the fuse size that is
the next higher. The fuse used for a circuit that has a total draw of 7.8 amps would be a 10 amp fuse.
Great!
ON YOUR OWN: Now I want you to try the next three problems individually (see handout).
Vocabulary: Let’s discuss the key terms associated with this system, before we try to understand how
they work together.
 Thermal switch – This component is located in the cooling jacket of the engine and is surrounded by
hot coolant. The thermal switch is made up of a set of electrical contacts fastened to a bi-metal strip.
As the bi-metal strip heats up in the surrounding coolant, the strip distorts and bends connecting the
contacts together completing the circuit.
 Fan motor – This component receives the electricity through the circuit and converts electrical
energy into mechanical energy rotating the fan and cooling the engine.
 Relay – The relay is the component that uses low amperage to control high amperage. Without the
use of relays, the wire diameters used in the vehicle would have to be of a large diameter thus
increasing the size of wire looms and harnesses. The components such as ignition switches, thermal
switches and other control devices would have to have high amp rated contacts which would increase
their size and weight. As the electro magnet in the relay is energized, it create and electro-magnetic
field drawing the high amp contacts together completing the circuit and providing a path for current to
flow to the motor, light or other load component. The magnet in the relay draws very low amperage (1
amp) so this circuit will be protected by the low amp fuse (10 amp). The Fan motor draws 30 amps
and the contacts in the relay are rated at 50 amps so it will be protected by the high amp fuse (50
amps). This way you are using a delicate 1 amp electromagnet in the relay to control the 30 amps
required by the cooling fan.
How the cooling fan circuit works:
The relay has the battery voltage already present at the low amp electro-magnet and the high amp
contacts. The magnet now only needs a negative for it to become energized and close the contacts. This
negative is provided when the coolant reaches approximately 200 degrees and the bi-metal strip in the
thermal switch bends and connects the contacts, completing the circuit. The high amp contacts in the
relay are now drawn together completing the circuit and providing a path for current flow for the fan motor.
Summary:
How many of you feel that you could confidently name the components of the electric cooling fan system
and their functions? Great! Let’s see…
Let’s name each component in the circuit: Teacher holds up each component, has the class write down
on individual white boards the name of the part and its purpose.
 Battery
 Fan motor



Thermal switch
Fuse
Relay
Evaluate:
Check for Understanding:
Now, using the Turning Point program, let’s recall the function for each one.
See Power Point...\Curriculum Folder\Cooling Systems\ELECTRIC COOLING FAN QUESTIONS.ppt
“Ticket Out the Door” – Students will answer questions about the electric circuit and turn in before they
leave.
Close: After this session and reviewing the ticket out the door slips, the teacher will decide if any areas
need to be re-taught prior to formal assessment.
This lesson will be followed with many “hands-on” activities, including: students successfully building a
circuit, troubleshooting a vehicle that has been “bugged” and in group discussions using “real world”
scenarios to learn the steps to solve problems in the automotive shop.
Formative Assessment:
It starts with determining prior knowledge by using the admit slips and their ideas for the electro-magnet
and the components. The assessment continues throughout the lesson with component identification and
ends with using the Turning Point Active Engagement System to check for understanding of the big
concepts. The students will also complete a ticket out the door slip at the end of the lesson to determine
if there are any gaps in their understanding and if any concepts need to be re-taught.
Related Materials and Resources:
Turning Point, Numeracy Handout.
Developed By/Contact Information:
Jeffrey Herman
Date Published: May 23, 2011
Submitted/Updated:
www.careertechpa.org
NOTE: This material was submitted in conjunction with the BCTE PLCs for purposes of
colleague sharing and may not be an officially endorsed or approved by PDE.
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