HVAC Sales Master

Fault Code Lookup

HVAC Sales Master
90 (SYS COM CRC)
Communication busy fault — SYS COM CRC / SYS COMM
This code typically points to
  • R & B to thermostat reversed polarity
  • Open/shorted data line
  • CCM communication error
Next checks to confirm
  1. Verify thermostat polarity
  2. Inspect data line for open/short
  3. Check CCM communications
Escalation
Information
Reset behavior
Clears when communication busy / CRC condition corrected.
Informational
No action needed
Source
Trane Hyperion *AM8/TAM8 Field Reference Data, p.22
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