I have an approx 10 year old GE S x S, model # GSS24SGMB BS. Several days ago it quit cooling effectively and temps started to rise on both sides. I just pulled the back freezer panel and the coils are completely frosted up. I've checked the thermistors with an ohm meter and they appear ok. I removed the defrost heater and it definitely needs replaced. The wire coil inside was broke.

The odd thing I noticed was that there's about 20 volts across the heater contacts with no heater installed. I thought this should either be 0V or 120V. The evap temp sensor showing way below 0F, so I'm wondering if the circuit board is trying to slightly warm the evap coils as the cooling cycle runs? Or is this a motherboard problem also? There's no defrost timer -- it's controlled by the main circuit board.

This is "leakage" voltage from some contamination. Once heater is installed it will go away.