dwh
Tail-End Charlie
Hard to test voltage when the cord is plugged in and fridge running.
Impossible without making an adapter or poking holes in the insulation. Even then, it's a bypass circuit and doesn't tell you what might be happening inside the fridge circuitry that you just bypassed with your meter.
The Art of Guesswork.
Maybe a clamp meter would work. I don't own one.
Nah, clamp meters measure amperage with the clamp, not voltage. Useful when combined with a voltage reading like the one the fridge is doing.
If the voltage reading drops, but the amperage reading didn't go up at the same time to account for it, then there's something dodgy in the appliance circuitry (or the wiring, but I'm assuming for the moment that you're right and there's no problem with the wiring (which is not an assumption that I would make if I was standing there looking at it...never trust the user, they lie, whether they know it or not )).