I have a TRANE XE 78. Here is what I have replaced thus far -
1. Board 50A50-405 with 50A55-486
2. Capacitor for blower
3. Transformer C340041P01 (was buzzing)
- Blower runs in high speed in "ON" position from thermostat indefinitely.
- Blower runs in "auto" position in call for heat mode. Board flashes rapidly. Furnace fire and runs perfectly.
- Blower runs for 20 seconds in "auto" position in A/C mode. Blower winds down. stops and then starts back in low speed. Copper on unit frosts up.
- Blower runs in "ON" position indefinitely until A/C mode turned on. Runs for 20 seconds, winds down, stops and starts back at low speed.
– After turning unit of at Thermostat and turning fan back to "ON" only, it will only run slow speed. If left off for 5 minutes, then turn fan to "ON" position it will run high indefinitely.
We have the same thermostat upstairs and down. I have switched. It is not that. I have checked and rechecked the thermostat to furnace wiring
and all checks out.
Is it the fan motor? Nothing else left. Thanks in advance. Tim