The mold heater is located under the ice cube mold and the connections extend into the support box, near the bottom. The heater is connected with two wires (labeled "A" below). The wires may be connected with slip-on connectors or the wires may lead to wire caps. Before disconnecting the wires, carefully label the wire placement.
Test the heater for resistance using a multitester. Set the multitester to the ohms setting X1. Touch one probe to each of the two terminals (or wires). The reading should be in the range of 60 to 90 ohms. If you get a significantly different reading, such as zero or infinity, then the mold heater is bad and needs to be replaced.