RUUD Air Handler with X13 Fan - X13SPD terminal never energized

rsc92

I have a RUUD Air Handler that utilizes the Protech 47-100436-02 control board.

This control board sends three 24VAC trigger wires to the ECM on the fan motor. One wire goes to the common terminal (from X13COM to COM terminal on ECM); one wire goes to the Fan Speed 1 program (from X13G on control board to terminal 1 on ECM); one wire goes to fan speed 5 (from X13SPD on control board to terminal 5 on ECM).

When I turn the fan on at the thermostat (without the system calling for heat or AC, the air handler motor cycles and 24VAC voltage is only coming from X13G which flows to terminal 1 on the ECM (X13SPD on the control board is NOT energized) – this is the low speed and as I have been told by a local serviceperson, this is what is supposed to happen.

However, when the system calls for heat or A/C on the thermostat with the fan either on auto or on, the air handler motor cycles and 24VAC is still only coming from X13G on the control board and as such, only fan speed 1 is initiated on the ECM.

When I check for voltage, I am getting 24VAC on the X13G terminal of the control board and get no voltage on the X13SPD terminal on the control board. As I understand it, when the system calls for heat or A/C and the t-stat is set to auto, the X13SPD terminal should electrify with 24VAC thus sending power to the ECM at terminal 5 and initiating the higher fan speed.

My question is whether or not the 47-100436-02 control board is bad or if I have another problem (i.e. wiring or t-stat).

I welcome and appreciate your input.

HVACNUT

Where are you located?
There's a Wiz for Rheem/Ruud at a distribution on Long Island.
Seems like the board isn't communicating with the ECM module.

John Mills_5

Whether or not the fan is set to on, anytime there is a Y or W signal for compressor or strip heat, it should switch to the higher speed. That's not happening?