Rinnai P70EV-713 HD70E Overheat Switch - Genuine Spare Part Don't even think about taking any shortcuts with the overheat switch - it's a vital safety component that's been put directly in the firing line on the heat exchanger. Its one job - and it's a job it takes very seriously: if the inside of the appliance gets too hot, it cuts the gas supply pronto. No heat exchanger gets nicked. No runaway overheating. No risk to the installation. The overheat bi-metal safety switch is right there on the heat exchanger, watching the temperature like a hawk and cutting off the gas supply as soon as it gets too hot. Most of the time it'll reset itself once it's cooled down - but if the problem that caused it to trip in the first place isn't sorted, it'll trip again just as soon as the temperature gets out of line. A Rinnai If you're seeing that cycling behaviour