Funnily enough I had planned to use a hair dryer for ten minutes (left pointing under the bed), but had a friend round so wasn’t in the cold garage very long.
Today decided instead on a hot water bottle. After looking at digikey.com for a replacement thermistor with a suitable value resistance at standard room temperature (~110 KOhm) I found that a standard 100.8K@25c NTC Thermistor from TDK has a resistance of ~310k at 0celcius which is what I was experiencing, and causing an error in recognition by the controller. It is 0.2celcius here today, so I tried using a hot-water bottle to warm the bed, and after ten minutes it booted and said 24celcius, and then I was able to tell the bed heater to turn on (30c first then 60). No replacement needed, just doesn’t like cold weather.
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