HVAC Sales Master

Fault Code Lookup

HVAC Sales Master
4
Open High Limit Device
This code typically points to
  • High limit open
Next checks to confirm
  1. Check high limit switch continuity
  2. Check airflow and filter if limit is tripping
Escalation
Gas valve closed / heating interrupted
Reset behavior
Depends on device state.
Safety Critical
Immediate concern
⚠ Cross-generation conflict
Legacy Code 4 was 'open limit'. The newer S-series e04 includes rollout and reverse-airflow switches in the same code — diagnostic path must branch on which device opened.
Source
Trane 18-CD19D2-18 Installer's Guide, p.23
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