I am installing a new two stage heat pump, rudd IUHPL. The 24 volt transformer is in the air handler. The transformer is energized and putting out 24 vt. Which enters the circuit board. The red wire leaving the board is 0 vt. As I understand the system this red wire is supposed to supply 24 vt to the thermostat and outside unit. Are my assumptions correct?
What conditions can cause this problem? The service books shipped with the units are not correct and do not include wiring diagrams or a help number to call at Ruud.

I'm not familiar with this model but some have door switches that won't allow the unit to operate unless the blower door is closed. Sorry, but that's all I can suggest without the diagram.

If you have 24 volts from the transformer in to the control board and not at the R and C on the board you have a blown low voltage fuse or open limit. Check the fuse first (3 or 5 amp automotive fuse center of the board).

If it is a true variable speed DC motor circuit you will also have to set the dip switches to match your system.