Hi All,

I have a 1 year old Trane XL20i / Hyperion 8 fully-communicating heat pump setup (TAM8A0C48V41 / 4TWZ0048A1 / XL900 / BAYEVAC10LG1AA) and woke up to find a red light on the thermostat with the ERR 104 error code. The manuals seem to describe this error as "Heather Relay Fault, Heater Relay Stuck Open / Closed". The air handler computer reports 4 alerts in history:

1. CNT FLF-HC AF
2. EH RLY WELD1 EH
3. EH LIM/NO AF
4. RLY WELD2 EH

The well meaning, but untrained (on modern communicating equipment and diagnostics) tech first stated that it is most likely a dirty airfilter... I'm pretty certain that restricted airflow doesn't cause this code and after showing him the clean filters and plenty of air supply he stated that the "heater relay" was defective and he would order a new one... I am thinking that something more can be had from these codes. Might you have any ideas as what else could be wrong?

The led lights from tip to bottom are as follows:

green - solid
amber - 3 blinks
green - blinking steady
blue - 1 blink
not lit
-----------
green - 4 blinks
blue - 1 blink
not lit

Thank you, Djyas