More on the installation, please.
Verify that you have no grounded wiring on any of the motor leads and that there is at least continuity between the common and other speed taps for the motor.
Once the basics are covered, then got to the T-stat put FAN to "ON" and then verify 24 VAC from the T-stat to the control board terminal on the G (or fan) terminal and then verify that the high volts are coming out of the board to the motor lead terminals.
Doing this will clear the breaker, fuses, transformer, board, T-stat, and motor.
Your hi speed lead should be connected to the proper terminal on the relay board , and the low speed will be connected to the fan relay side for heat (n/c), as it will be regulated by the sequencer program in the board. The white motor wire should be connected to L2 somewhere. The medium speed wire can be taped off. The ICM board should have dip switches on it that must be programed according to the installation. The Install manual should show this.
JW, I'd like to have my questions answered before you throw the subject off on a tangent, thanks. On second thought, I'm going to let you walk this gent thru the problem. You apparently have the experience needed to handle this by yourself...