Where is the defrost timmer in a sub zero 650

I'm not seeing a link to the technical/repair sheet on their website (Sub-Zero 650 Over-Under Refrigerator/Freezer: Sub-Zero Built-In Refrigeration) , but I bet if you called them, they'd send you one or give you a link.

Otherwise, double check on the rear of it... the technical sheet might be taped to the back of the unit.

Stay tuned, though, we have good Appliance experts here: they might be able to tell you more specifically.

Try http://www.subzero.com/resources/products/downloads/600ucguide.pdf . This unit has an electronic defrost timer and usually will not fail, but the same cannot be said about the defrost heater in the freezer coils or the defrost terminator. I would check these if you have a problem, further, make sure you clean the condenser coils. Soap and water works best; just be careful to unplug it and vacuum up water. DrTom4444