Before troubleshooting, you must know the baseline specs found in the service manual:
Unlike modern devices that are often "throw-away" technology, the Gordak 952 is repairable. However, opening the unit reveals a PCB that can be confusing without a map. A service manual provides: Gordak 952 Service Manual
If the display jumps around or shuts off randomly, the issue is usually the thermocouple inside the handpiece. The schematic in the service manual will show the resistance values you should expect to see at the connector pins, allowing you to diagnose a broken wire versus a faulty PCB sensor. Before troubleshooting, you must know the baseline specs
The service manual schematic shows the path: Live -> Fuse -> Relay -> Heater -> TRIAC -> Neutral. Safety warnings from the original service manual:
Since Gordak does not provide a public direct PDF link, here is how to assemble your own service manual:
Safety warnings from the original service manual: