⚡ Essential Reading
Common Symbols in Electrical & Technical Diagrams
A complete visual reference for the symbols used in wiring, schematic, and parts diagrams.
In This Guide
Basic Electrical Symbols
These foundational symbols appear in virtually every type of electrical diagram.
| Symbol | Name | Description |
|---|---|---|
| — | Wire / Conductor | A conductive path carrying current between two points |
| • | Junction / Node | Two or more wires are electrically connected at this point |
| ⏚ | Ground (Earth) | Reference zero-volt point; return path for current |
| ═══ | Battery | DC voltage source; long line = positive, short = negative |
| ⊕ | Positive Terminal | Higher-potential connection point |
| ⊖ | Negative Terminal | Lower-potential / return connection point |
| ◎ | Lamp / Light Bulb | Load that emits light when current flows |
| △ | Fuse | Overcurrent protection device; breaks circuit when overloaded |
Switches & Controls
| Symbol | Name | Description |
|---|---|---|
| —/— | SPST Switch | Single-pole single-throw; basic on/off switch |
| —\— | SPDT Switch | Single-pole double-throw; toggles between two circuits |
| ⊙ | Push Button (NO) | Normally open; connects circuit when pressed |
| ⊗ | Push Button (NC) | Normally closed; breaks circuit when pressed |
| ↕ | Relay Coil | Electromagnetically-operated switch |
| ◁ | Relay Contact | The switched contacts controlled by a relay coil |
💡 Tip
In automotive diagrams, relays are often shown as a combined coil + contact block. Look for a box with both the coil symbol and the switch symbol inside it.
Passive Components
| Symbol | Name | Description |
|---|---|---|
| ≡ | Resistor | Opposes current flow; limits voltage and current |
| ⊐⊏ | Variable Resistor | Adjustable resistance (potentiometer, rheostat) |
| || | Capacitor | Stores electrical charge; blocks DC, passes AC |
| ⋊⋉ | Inductor / Coil | Stores energy in a magnetic field; opposes AC changes |
| ①② | Transformer | Transfers energy between circuits via magnetic coupling |
Active Components & Semiconductors
| Symbol | Name | Description |
|---|---|---|
| ▷| | Diode | Allows current in one direction only |
| ▷Z | Zener Diode | Voltage regulation; conducts in reverse at set voltage |
| ▷) | LED | Light-emitting diode; emits light when forward-biased |
| M | Motor (DC) | Converts electrical energy to rotational motion |
| G | Generator / Alternator | Converts mechanical energy to electrical energy |
Automotive-Specific Symbols
Automotive wiring diagrams use a mix of standard symbols plus manufacturer-specific notations.
| Symbol | Name | Description |
|---|---|---|
| ⬡ | Connector Body | Physical multi-pin plug/socket |
| C12 | Connector Reference | Labels like C101, C202 identify specific harness connectors |
| S14 | Splice Point | Location where multiple wires join inside harness |
| G101 | Ground Point | Specific chassis ground location (numbered for tracing) |
| F5 | Fuse Reference | Refers to fuse #5 in the fuse/relay box |
Plumbing & HVAC Symbols
Plumbing and HVAC diagrams use their own symbol set, separate from electrical conventions.
| Symbol | Name | Description |
|---|---|---|
| —⊗— | Gate Valve | On/off flow control valve |
| —⊕— | Ball Valve | Quarter-turn shut-off valve |
| ▽ | Floor Drain | Drain point at floor level |
| ○— | Water Supply | Cold or hot water supply line |
| ~~ | Flexible Hose | Flexible connection between components |
| △▽ | Heat Exchanger | Transfers heat between two fluid circuits |