Phase B diagnostic tool
Electrical Control-Path Helper
Only trained persons using appropriate PPE, meter category rating, and safe procedures should perform energized testing. De-energize and verify absence of voltage before resistance checks. Never assume wire color identifies function.
This tool organizes observations into possible causes and confirmation tests. It does not provide a confirmed diagnosis, replace manufacturer information, or authorize unsafe operation, component replacement, or refrigerant adjustment.
Possible path
Rated voltage across the contactor coil with no pull-in may indicate an open coil, wrong coil rating, or mechanical binding after measurement verification.
Confirmation
Verify reference points, meter operation, schematic, equipment state, and voltage under load. Do not assume wire color identifies function.