Abstract: A resistance welding system with a self-contained close-loop cooling arrangement which includes a chiller, a welding transformer, a cable and a welding gun. The chiller has a feed-port and return-port for the cooling fluid. The welding transformer has an inlet and outlet for a defined cooling path and the inlet is coupled with the feed port of the chiller while the outlet is coupled with the return port of the chiller. One end of the cable is connected to one side of the transformer, for carrying the welding current. The cable is capable of being coupled to the chiller in a manner to internally transfer the cooling fluid in either direction. The welding gun is connected to the other end of the cable and has a pair of electrodes for applying the current through a pair of workpieces. The welding gun also has a built-in cooling system which is capable of receiving, circulating and returning the cooling fluid to the chiller without external fittings and hoses.