HVAC Sales Master

Fault Code Lookup

HVAC Sales Master
9
Check Ignitor circuit and Line N to 24VAC Common voltage (<2 volts) — possible grounding problem
This code typically points to
  • Ignitor circuit fault
  • Line N to 24V common voltage relationship out of range
  • Grounding problem
Next checks to confirm
  1. Check ignitor circuit continuity
  2. Measure Line N to 24VAC Common voltage (should be <2V)
  3. Verify grounding
Escalation
Ignition/no-heat fault
Reset behavior
Clears when ignitor/grounding issue corrected.
Urgent
Fix now
⚠ Cross-generation conflict
Code 9 means completely different things across Trane/American Standard legacy platforms. On UD2/DD2 and UC1/DC1, it's an ignitor/grounding fault. On AUY/TUY and AUH2/TUH2, it's an open inducer limit — totally different diagnostic path. Your model prefix determines which it is.
Source
Trane 18-CD19D2-18 Installer's Guide, p.23
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