3 ph fan motor

[SimonLW]

I was checking the roof units for clogged condensor coils and non working
fans (each unit has three fans). I found one fan operating at what seemed
like half speed. It was not making any unusual sounds.

Would an open phase in the motor cause this?

Thanks -S

 

[Bob]

Yes, and it will burn up if left that way. HURRY! Just so you know
however, the open phase could just be a blown fuse in the circuit
somewhere.