York Rooftop Unit: ZF Re: Ignition Lockout Codes Light Status Description Off No Power On Control Failure - Replace Control Heartbeat Normal Operation - No faults 2 Flashes Pressure switch stuck closed 3 Flashes Pressure switch failed to close ...

York Rooftop Unit: ZF120 Re: Heat Board - Code 3 If, after the induced draft blower is energized, the pressure switch circuit does not close, the control will keep the blower on and wait for the switch to close. The diagnostic code for this problem is 3 short flashes followed by a pause. ► The...