My Dick Smith T-2000 soldering station must be about 30 years old now. Over the last couple of years it developed an intermittent problem where the temperature meter would dive to zero and the heater would switch on keep heating without switching off. Wiggling the cable into the handpiece temporarily fixed the problem.
Today the problem got so bad that I had to do something about it.
I figured the problem was a frayed or broken wire interrupting the temperature sensing circuit so I cut off about 10cm of cable at the handpiece end and re-attached. Problem solved! Checking the removed wires however didn't show any obvious breaks etc so perhaps it was a bad solder joint in the handpiece and it was the re-soldering that actually fixed it?