Diagnosing car AC electrical faults requires systematic wiring diagram analysis. Below are common errors and solutions:
Key Wiring Diagram Symbols
Decode these critical symbols before troubleshooting:
- Solid Lines: Direct wire connections
- Dashed Lines: Mechanical linkages
- Triangles: Ground points
- Numbered Circles: Connector reference points
Common Electrical Failures & Fixes
Blower Motor Inoperative:
- Check fuse continuity (diagram location: Fuse Box Section)
- Test resistor block continuity per resistance values in diagram notes
- Verify 12V at motor connector when set to MAX (key ON)
Compressor Not Engaging:
- Confirm pressure switch closure (diagram: Safety Switches)
- Measure voltage at clutch coil (diagram: Compressor Circuit)
- Inspect relay control circuit for ECM signal (diagram: Control Module)
Erratic Temperature Control:
- Test blend door actuator feedback signal (diagram: HVAC Module)
- Check potentiometer resistance values against diagram specifications
- Trace short circuits in harness near heater core
Diagnostic Protocol Using Diagrams
- Identify circuit architecture (diagram section: AC Control)
- Perform voltage drop tests across connectors
- Verify ground paths using continuity mode
- Cross-reference wire colors against legend
Critical Safety Checks:
- Disconnect battery before handling PCM connectors
- Use fused jumper wires for relay bypass testing
- Replace damaged connectors entirely - avoid splicing
Focus tests on diagram-identified junction points. Most electrical failures occur at connectors, grounds, or protection devices.