Just replaced the wafer thermostat in both Hovabators. There was some fluxuation but not all that bad, or so I thought. The wafers were 20 years or so old. I still don't know what to look for as far as them being bad, but changed them from advise I got here. They did keep a more accurate temp after install. Question though, is new wafer and now new switch or only when that would "go" and the temp sky rockets because it didn't trip? Thanks for your help.