Grab N Win uses a DC motor to drive the crane forwards and backwards. Under normal operating conditions during the start up routine the crane will check the state of the front sensor by driving the motor forward. The main board waits from the response from the magnetic sensor on the front of the assembly if the sensor signal is not seen within a period of time the game will generate an error 4.
The motor is connected to the P1 connector on the main board between pin 10 (blue wire) and 13 (yellow wire). To test the output from the main board place your multi meter probes between the two pins and set your meter to DC voltage. Coin the game up and press the joystick forwards you should see ~8 to 12vdc , when you reverse the direction of the joystick the voltage should reverse polarity.
Crane assembly (top removed)
The game determines when the crane assembly is in the front position when the magnetic reed sensor meets the magnet located on the wagon assembly. To test the sensor place your probes between pin 11 (white wire) and pin 7 (black wire). When the sensor and magnet are apart you will see 3.3vdc and when they are together you will see 0vdc. If the signal for the sensor is low at 0vdcc the main board will disable the ability to move the motor forward.