Customer has now decided to get a new oven but would welcome any pearls of wisdom anyone can offer.
Bottom oven switching on but after running for a bit the “oven on” and temp lights go funny, being on when they shouldn’t and off when they should when turning the temperature knob. Found fan element had low resistance, grill element in same oven not too good but not too bad either when I first checked. So replaced the fan element, but fault persists. Turns out the grill element’s resistance is worse than when I first checked. Potentially changing the grill element would fix it, however it’s difficult to get and as mentioned customer has given up and is getting a new oven.
What I find puzzling is that the overall insulation of the appliance is only 15 MOhms (with faulty bottom grill element disconnected). Though safe, seems fairly low and I can’t trace it to a particular component.
Wiring seems to be in good order and power to the oven is fine.