VDR is a varistor (has no resistance) placed in parallel with the power supply (AC or DC)
SCK is a thermistor (has a resistance) placed in the gap (as a current limiter) of the power supply.
It is from Galmet wood pellet boiler controller.
Apparently it was left switched on all summer in tripped state. When it trips the LED backlight is not visible so looks switched off. Wood pellet boilers this year are very popular in our region.
I can’t say for sure (I need a datasheet) somewhere they write 080 - 80mA, but somewhere it’s 800mA.
But 0.08A is some very small current for this block.
It seems to be 250V 80mA hold, 160mA trip PTC fuse, 6.5mm dia. Sea & Land Electronic corp. C250-080
There is something else shorted for this PTC fuse to heat up and die. I would look for a problem in the power supply section.
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