"What should I look for?"

You won't be able to find what is invisible. R134(coolant/gas). If the compressor and everything else seem to be working, I would say the compressor will need recharged. This won't be cheap, around $300-$400

Any way of easily telling if R134 is low? I recall years back with some compressor telling if it was charged by the temperature of some line... but that was when dianasours roamed the streets.

I'd really like to keep this box going for awhile. Is there anything I can check on it?

Just took this photo. It's been a week since a full thaw which included just letting it sit for three hours while the mullion (part between the refrigerator and freezer) thawed. Thought a photo might help.

Here is a link that might be useful:

If you're getting 680 watts during defrost, then the defrost heater apparently is working ... unless it's partially shorted and not heating along the full length.

The refrigeration system (compressor, evaporator, condensor) is sealed and needs recharging ONLY if there's a leak somewhere, which must be repaired or it'll simply leak out again.

Are both the evaporator and condensor fan running?

Torn gasket on one of the doors, allowing excess moisture in?

If you manually trigger defrost by turning the timer, does it defrost properly? You'd have to put the evaporator cover back in place to test that so the defrost heat is directed across it correctly.

Just finished defrosting it again. My wife cringes when I ask to borrow the hairdryer... could write some entertaining stories about that one.

Both fans are running and the door gaskets are in good condition. Tonight I marked a 12:00 position on the defrost timer dial to make sure it's actually turning on it's own. I know advancing it manually triggers the defrost cycle. All circuit connections I see appear intact. Based on the "clicking" or "expanding" sounds I'd assume the heater is fully functional. I'll scan it with my infrared thermometer and post result later.

Gee, not to sound like a fool but a few days ago when I checked with the killawatt device the defrost cycle was clearly drawing some 600 watts. This evening, it's zero. Nada. As expected, it goes to 40 if I open the door. Should I suspect the timer first, or something else?

The defrost heater may not necessarily activate, even by manually triggering the timer, if the defrost control thermostat isn't cold enough. If you've done a manual defrost and the unit hasn't run long enough to chill the coil down, the defrost 'stat may not yet have "recovered."

Yes, that is correct. This has become quite a lesson for us.

I see now that the with the refrigerator in use again that the heater is now drawing several hundred watts, and looking at the schematic it would appear that the bimetal switch might have been open because the unit was at room temperature.

What would you suggest I look into next?

And thank you for your help...

I found the bimetal unclipped from the freezer line, and after securing it to the coil waited several hours for a defrost cycle to take place.

I was monitoring it with a killowatt device to tell when the heater kicked in. When the bimetal caused the heater to turn off, and before the timer caused the compressor to start again, I unplugged the box and removed the rear freezer panel. With an infrared thermometer we saw the bimetal was around 50 degrees. There was still some frost present on the coil, top center area. Is that a normal cycle?

I'd still like to replace the bimetal only because the clip doesn't appear secure. The refrigerator's service sheet calls for a 2183072 which is listed as being interchangeable with 4387503, 2149641, 2149643, 2163894, 2172694, 2182380, 2221677, 4343917, 4387503 and the one the local store has which is 4387490. Is one preferable?

4387503 appears to be the current crossover. 2183702 substitutes to it.

4387490 appears to be a different item. At the online parts source I normally use, it does not indicate a substitute to 4387503. Depends on if the cut-in/out and differential are the same.

Bimetals usually either work or not. Sounds like yours may be OK, unless it's erratic. Can you determine if you clipped it back in the correct/original position on the evaporator? In some cases of the coil being very heavily iced, it may not fully clear in the allotted defrost time, but it should under normal conditions. The bimetal's function is to turn off the element if/when the frost clears before the allotted timer cycle is finished, but it doesn't (usually) stall the timer if a longer cycle is needed.

I think it's working, time will tell. I found the bimetal switch loose and behind a clump of wires in the top left corner. Tried pinching the clips together a bit and securing it to the aluminum tubing just before it transitions to copper, but the clip's prongs have no strength and it just falls off. But for now it's sorta wedged in place. Will find either the OEM 2183072 or a 4387503. All the local place had was a 4387490 which they said was interchangeable, so I'll search elsewhere. Glad you had the correct information; I saw online that 4387490 opens 8 degrees earlier (42 vs 50) than the others.

My killawatt device is showing that the heater is turning off a about five minutes before the timer switch tells the compressor to begin. I think the heater should be on for a longer time. When it completes a defrost cycle, there's still some buildup present on the coil just below the fan and in the top right corner near the duct. Was thinking of repositioning the replacement switch to one of those areas, but also have respect for the Whirlpool engineers design. What should I do about the remaining frost?

To help in that direction, I see that the current timer (2162052) is 10 hours and that the replacement (please recommend the proper replacement as they also seem to abound) are typically 8 hours.

I replaced the bimetal with a 4387503 and, after allowing it a few days, the defrost seems to be working fine!

Still want to replace the obsolete 2162052 10 hour timer while it's easy to access. Would be happy to replace it with an 8 hour timer -- which model is recommended?

I replaced the bimetal with a 4387503 and, after allowing it a few days, the defrost cycle seems to be working fine!

Still want to replace the obsolete 2162052 10 hour timer while it's easy to access. Would be happy to replace it with an 8 or 6 hour timer -- which model is recommended?