My 2000 plus is stuck on high speed since a recent thunderstorm. I have disconnected the red wire from the smaller of the two boards to the number two relay, and it works on low speed now. Does this mean I need this board ?
Is it the B,G,Y,R wires you disconnected? The red wire may also be the low speed fan wire. Orange for High speed and Blue for Medium. Make sure both fans are still running.
Do you use a wall control and if so what kind?
If you disconnect all the wires on the HRV and jumper B and G, the high speed fan should run and the damper should open. Usually this means the control board is not defective.