Refrigerator diagnosis sought

No lights came on when refrigerator door was opened this afternoon. Up to then, no sign of a problem. Electronic control panel also completely dark. Light on in freezer compartment, though. Pressing "unit on/off" touchpad produced no effect in refrigerator. No air flow/noise from condenser underneath. Depressible door sensors moving freely.

Perusal of owner manual mentioned unit may be "in defrost" if "not operating". Manufacturer website indicated refrigerator defrosts during each off cycle of refrigerator compressor. This behavior quite different, though - never observed before in 15 years of use. I don't think it was in defrost.

I waited 40 minutes before opening refrigerator door again. Electronic control panel is now lit up; lights in compartment back on, too. Control panel says refrigerator compartment temperature 59F; freezer 0. Still no activity in condenser area. Closed door; wait 15 minutes before re-open. Temp 61.

I press "unit off" at control panel, wait 10 minutes, then turn it back "on". Compressor comes on. Refrigerator temp has now returned to 38.

Any ideas what happened?

What's the brand/model? Any unusual events recently, such as door left open overnight?

15 years is a good long time for an appliance with digital electronics built in. You'll see the control panel fail before the compressor and it looks like temperature sensors are probably OK.

With the info provided, my first guess would be the low-voltage power supply to the control panel can no longer supply enough current to run the display and lights. I'm assuming your lamps are not incandescents because you would have tried to replace them. The low-V board probably supplies 48/24V to the lamps and 5-12V to the logic board. On well designed equipment that should be the first thing to blow. Sometimes you can replace the filter caps to buy yourself another 2-5 years on it.

It may also be the door switch that tells the control panel the door has opened/closed - some units use that data to determine the length of time for defrost. The switch could be bad, someone could have left it open, or open/closed it 1,000 times in 1 day. If it runs fine now it was probably that - if the lights and panel fail again check the low voltage power supply.

There was a power outage, not long, this morning. Could that have had any impact? (I ask because the last one we had made the clock and timer on our stove go wacko - after today's failure, I reset - again - and they are both working normally now (after 2 weeks of being totally off time).

Thank you.

In answer to questions: subzero 700 series. Through the years, door has been left ajar a few times, including about 1 month ago. Lamps providing interior illumination were replaced about 1 year ago - I recollect there were "regular" incandescent. Upon questioning, Ms. dickf3 tells me she has experienced a completely dark refrigerator compartment upon door opening "a few times"; her solution was to close the door and go away. Upon return, "everything was OK". I just learned this now.

http://www.subzero-wolf.com/trade-resources/product-specifications/product-specifications-detail-page?name=27-inch-integrated-over-under-refrigerator-freezer-panel-ready

Sounds like the bulbs are maybe fine but are getting intermittent power - I would do the easy check of the switches first. If you had low-voltage bulbs then I would suspect the power supply first - but the manual says it takes regular old 120V 40W in some spots and 25W in the drawers

Yes: regular old appliance bulbs 120V 40W are what I replaced.

2 Questions:

What is entailed in a switch check? I've depressed the depressible protrusions (mimicking door closure) and then released them (door open) a few times- lights/control panel darken/light up normally. Is this enough to be confident it wasn't a door switch problem?

And: if it IS a switch problem, would that also explain both the control panel initially not lighting up (I'm thinking yes), and the compressor not kicking in at 61F (until, later, after I turned the unit off, and then back on)? On the latter one - I'm thinking no. (I'm no engineer)

In response to cody's suggestion above: good idea; I don't know.