This is a 1979 Whirlpool refrigerator, model EET-172PK.

I was in the kitchen for a couple minutes this morning and noticed
that the compressor was attempting to cycle ON about every 20-25
seconds, but only staying on for maybe 3 seconds. The evaporator
fan motor feeding the freezer compartment was running
continuously, cool but not icy. The condenser coils were not hot
to touch as they normally would be when the compressor is on.

So I quickly cleaned the dust out of the condenser coils, but that
didn't change anything. So I thought that for whatever reason
there wasn't enough freon for the compressor to run.

Then after a few more minutes, the compressor turned on, and stayed
on, and appears to now be running fine - hot condenser coils and
all. It has now reached the trip point of the thermostat, and
turned off as it normally does.

So I'm wondering if maybe this is what's happening: this morning I
caught it in the middle of a defrost cycle, when the compressor and
fans should have been off, but weren't. So there may be a switch,
or a clock of some kind that controls the defrost cycles, and it's
not disabling the compressor fully during defrost like it should,
but there's an additional backup safety switch that's shutting down
the compressor when the heating coils are hot.

Does this sound reasonable? If so, is it possible to get to the
defrost clock and switches? Where would they be? And is it
possible to get a replacement for whatever assembly that is, or
even fix it? I have this image in my mind of a switch carrying
power to the compressor that's supposed to open during defrost
cycles (cam-driven, probably), but is fused closed. Or maybe
there's some crud in the way. Or maybe a cam lobe broke off.

Anyway, what do you think?