Re: in-line heater test?
no such luck.
The wires from the heater run to a plastic pressure sensitive relay

A small hose runs from the sump to the takeoff point shown.
It appears to trip given a very small bit of positive air pressure so I guess the water in the sump forces air down the tube to the relay.
Anyway checked it and it seems to opporate ok and the pipe seems clear.
The wiring starts to get a little more complicated now 😯
I gave AEG a ring and they said that there was no thermostat but there was a sensor but their diagram did not show where it was 😡