The white wire (upper left) on the timer is not needed for a "regular" SPST switch. The black wire (power from breaker box) should go to one of the switch terminals and the red wire (switched power to fan) to the other switch terminal. The neutral wire passes through from breaker box to fan (wires in yellow wire nut).
It sounds like the grey wires may go to the fan but I can't be 100% sure. If they are the fan wires, one will go to neutral (yellow wire nut) and the other to the switched side of the switch (red on the timer).
If the bathroom is an add-on, there may be a separate breaker box for it.
Last edited by SouthArk370Z; 09-29-2015 at 08:23 AM.
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