A welder was experiencing problems with the governor control on a portable welding machine. The welder lifted the shroud at the radiator end of the welding machine and was wiggling some electrical wiring when he received a 12-volt shock. His natural reaction was to jerk away and when he did, he hit the radiator cooling fan cutting his ring finger on his left hand. It was later determined to have caused a hairline fracture. He returned to work following x-rays and a bandage.