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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Getting error code 91 on acculink thermostat (same as trane

Customer Question

Getting error code 91 on acculink thermostat (same as trane comfortlink II). Heritage 20 compressor and 4TEE air handler. Fault LED is flashing three times and the comm LED is flashing fast. User Interface Display says SYS COMM ERR. Alert Code Addendum chart shows this is a Comm heat/cool demand error. Any idea what the issue may be?

Thanks,

Steve
Submitted: 7 years ago.
Category: HVAC
Expert:  BillyHvac replied 7 years ago.
<p>I would have the staging checked. The sensor/thermostat has asked for something...and did not get what it wanted...thus the fault. I would start with the ac staging...check refrigerant and engage full operation.</p><p> </p><p>I am available for follow up.</p><p> </p><p>Billy</p>