Trane XR80 fan doesn't work in any mode

[Doug B]

Hi.  I have a Trane XR80 gas furnace that recently stopped working. The blower fan doesn't start.  All I hear is a faint humming. 

I followed this archived thread to troubleshoot the issue.  I have replaced the run capacitor and the blower motor, and still nothing.  What else can I try? 

 

Thanks

[Sctronics]

What motor is not running?

[Sctronics]

Does the the unit fire up “start heating”

[Sctronics]

Have you tried the fan setting on the thermostat? Pull a wire off the high limit and see if the blower comes on. I could be a bad control board.

[Doug B]

1 hour ago, Sctronics said:

What motor is not running?

The main fan blower -- I guess you'd call it the air handler?  I don't think the furnace fires up, but I'll double-check that.  The fan doesn't operate even if you turn the fan on in manual mode at the thermostat. 

[Sctronics]

Make sure you have all the proper voltages. That slight hum is probably the transformer. Check foe 24 volts at the r and c terminals.

[Sctronics]

Also check for a blown low voltage fuse if it has one. I’m not  familiar with that furnace.

[Gasman74]

Check the door switch.Trane doors are a PIA. With the tstat calling for heat the burner circuit should turn on first.Unless the door switch is off.If the switch is good plug power from door switch into black leed from motor(high speed).if the fan turns on problem is on the board.