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
  • Grounding problem
  • Improper N-to-24VAC common relationship
Next checks to confirm
  1. Check ignitor circuit
  2. Measure Line N to 24VAC Common (should be ≤2V)
  3. Verify grounding
Escalation
Ignition/no-heat fault
Reset behavior
Clears when 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-CD19D5-21 Installer's Guide, p.37
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