This unit will operate without the dash and meter print board installed so that leaves something to do with the rear end of the unit or directional wiring from steer colunm to dash. when you say display blank do you mean it lights up with no characters or doesn't illuminate? With key switch on does forward and reverse contactors close? If dash does not illuminate, check seat switch wiring and cabin relay located next to horn relay underneath floor board. Let us know what you find after these checks,