Fault route
CT-312 Fan Not Running or Auxiliary Power Missing Diagnostic
A CT-312 bottom-board support route for fan or auxiliary-supply failure.
Quick Answer
Fan or auxiliary power faults belong first to the CT-312 bottom-board support layer. Check input, relay/start path, fan socket, auxiliary supply and control-power support before diagnosing TIG/plasma mode faults.
Diagnostic path
Input supply → relay/start path → auxiliary supply → fan socket → gas/HF/control support.
Evidence table
Fan dead with no control support: bottom-board auxiliary path. Fan socket voltage present but fan dead: fan or wiring. No gas/HF plus no fan: shared support layer.