Interactive Vehicle Wiring Lab
Interactive Vehicle Wiring Lab
Operate the circuit, watch current paths change and diagnose faults with a digital multimeter.
Why voltage on the ground side exposes a bad ground
Establish a loaded circuit
Turn the headlights on and leave low beam selected. A voltage-drop test must be performed while current is flowing.
Relay common
Usually the power feed entering the switched side of an ISO relay.
Normally open
Connected to terminal 30 only after the relay coil is energized.
Normally closed
Connected to terminal 30 while the relay is relaxed. The fog cutout uses this path.
Relay coil
Current through the coil creates magnetism that moves the contact arm.
Complete Diagnostic Simulator
Learn the system, test the circuit, find the fault and prove the repair.
Test results
- No tests performed.
Relay-controlled work lamp
Connect the terminals to create a safe relay-controlled lamp circuit. Select one terminal, then another, to install a wire.
Component tray
Click a component to add it to the bench.
Choose the measurement before connecting
DC voltage is measured in parallel with the powered circuit. The meter has high internal resistance and applies very little load.
Operate a five-terminal relay
At rest, 30 connects to 87a. When the coil is energized, the arm moves and 30 connects to 87.
Interpret loaded readings
| Test | Training guideline |
|---|---|
| Connection | Near 0.00 V |
| Ground path | Generally below 0.20 V |
| Power path | Generally below 0.50 V |
| Starter cable | Use manufacturer specification |
These are teaching guidelines, not universal service specifications.
Load the circuit
A high-resistance connection may pass enough current for a DVOM to display system voltage with the load disconnected. Operate the load and measure voltage drop across the suspect path.
System proficiency
Recent results
- Complete a diagnostic case to begin recording progress.