CAR Blueprint Reading & Interpretation 3 — Questions and Answers
Question 1: On a dryer wiring diagram, terminals labeled L1 and L2 represent:
- Low-voltage and line-voltage circuits
- The two 120V legs of a 240V supply (Correct answer)
- Left and right heating elements
- Load 1 and Load 2 relays
Correct answer: The two 120V legs of a 240V supply
L1 and L2 are the two hot legs of a 240V split-phase supply, each carrying 120V to neutral.
Question 2: In a blueprint title block, the 'revision history' section is important during recycling assessment because it:
- Lists the appliance's serial number
- Records design changes that may affect component compatibility (Correct answer)
- Shows the refrigerant charge weight
- Provides the model's energy star rating
Correct answer: Records design changes that may affect component compatibility
The revision history documents changes to the design, which is critical when sourcing replacement parts or assessing material composition.
Question 3: A schematic shows a component symbol with two parallel horizontal lines of unequal length. This represents a:
- Capacitor
- Battery or DC power source (Correct answer)
- Transformer winding
- Fuse
Correct answer: Battery or DC power source
Two parallel lines of unequal length is the standard schematic symbol for a battery or DC power source, with the longer line being the positive terminal.
Question 4: When interpreting a heat pump blueprint, the reversing valve is identified because it:
- Is the only component with a capacitor symbol
- Has four refrigerant line connections shown on the diagram (Correct answer)
- Is labeled as the compressor bypass
- Is always drawn in the center of the schematic
Correct answer: Has four refrigerant line connections shown on the diagram
A reversing (four-way) valve has four refrigerant ports — suction, discharge, and two to the indoor/outdoor coils — which distinguishes it on diagrams.
Question 5: A CAR technician reads a blueprint scale of 1:10. If a component measures 3 cm on the drawing, what is its actual size?
- 0.3 cm
- 3 cm
- 30 cm (Correct answer)
- 300 cm
Correct answer: 30 cm
At a 1:10 scale, the actual object is 10 times larger than the drawing, so 3 cm × 10 = 30 cm.
Question 6: On an appliance schematic, a component labeled 'OLP' is typically found protecting which part?
- The timer motor
- The compressor motor (Correct answer)
- The defrost heater
- The door switch
Correct answer: The compressor motor
OLP stands for Overload Protector and is mounted on or near the compressor to cut power if the motor overheats or draws excessive current.
Question 7: Which blueprint view shows the appliance as if cut horizontally to reveal interior shelf and compartment layout?
- Front elevation view
- Isometric view
- Horizontal section (plan) view (Correct answer)
- Detail view
Correct answer: Horizontal section (plan) view
A horizontal section or plan view cuts the appliance at a horizontal plane to show compartment arrangement from above.
CAR Blueprint Reading & Interpretation 3
On a dryer wiring diagram, terminals labeled L1 and L2 represent: