How do I wire an intermatic t-103 timer switch

The T-103 has a 120Volt clock motor

From there, the wiring can go two directions depending on your Load voltage (load is the fan, light or motor that timer turns on-off)

Here is a link that shows exact wiring:
http://waterheatertimer.org/How-to-wire-T104-Intermatic-timer.html#T103

When wiring the T-103, steps 1-2-3 are true for 120V or 240V installation:
1) A white Neutral wire is always connected to terminal A (Neutral wire connects to Neutral busbar in breaker box)
2) A black Hot wire is always connected to terminal 1 >> this hot wire can come from 120V or 240V breaker
3) Black wire going to Load (fan, light, motor) is always connected to terminal 2
The following step is true for 120V Load
4) if Load is 120V, then white wire from Load connects to terminal A
The following steps are true for 240V Load
5) Only the neutral wire connects to terminal A as described in (1
6) The second Black hot from breaker box (240V has 2 hot wires) connects to terminal 3
7) The second White going to Load connects to terminal 4

Here are 2 more links that show how 120V and 240V circuits are wired
http://waterheatertimer.org/See-inside-main-breaker-box.html
http://waterheatertimer.org/B220C.html