What is this?

[Ruzzell]

Does anyone know what these things are? We keep digging these old things up in our yard. They appear to be a hard plastic with some kind of electronics inside them. Thanks.

 

[Lucien Nunes]

I think they are bimetal thermostats for the fridge evaproator defrost heaters. Many fridges now use a thermistor controlling an electronic thermostat instead, but some models are still bimetal. The heater is a sheathed element threaded through the evaporator and the thermostat is strapped amongst the fins. It's sealed into the tube as it gets dripped on when the ice melts.

Typically, the defrost timer switches the compressor and fan off and the heater on, Then, once the ice has melted, the thermostat opens and restarts the timer motor in series with the heater. Some have another contact for the timer. See pic:

Fridge defrost thermostat

 

[DPG]

I suspect Lucien is right. I reckon kids got hold of these years ago and just connected them all together and buried them for something to do. Of maybe even to confuse people (like us) in years to come.

Great thread.

 

[marconi]

So the prize goes to Westward10?

 

[Marvo]

The bi-metallic thermostat theory has a few clouds over it for me, firstly he's found multiple of these items in the same area over time and I can't imagine any application that would result in numerous bi-metallic thermostats being left around. Secondly I'm doubting these things were 230v or even US 110v because one of the wires is connected to the outer metal body which means this thing would have been outdoors at mains voltage with no protection other than a heat sealed plastic sleeve.

I'd guess some type of ELV switch like maybe a vibration sensor for a very old perimeter alarm.

 

[Lucien Nunes]

They are from fridges, they aren't meant to be outdoors! No idea how they came to be there; soneone's stock got dumped somehow, maybe kids as per DPG.

 

[PEG]

I'm with Lucien,on this.....simple devilment...

It's the reason i dug up the Blue Peter time capsule,and swapped the contents for a teddybear,holding an AK47

 

[Ruzzell]

Thanks, all. Seems like most votes are for thermostats, in which case they must have ended up there somewhat randomly. No reason for them to be there. Maybe kids found a box of them and buried them. Marconi's suggestion made more practical sense, because this tree and area around it is thronged with chipmunks, mice, and squirrels, which we trap and shoot every year because the tree is right next to our garage, which gets infested. Hew berries are a favorite of the rodents. Guess we'll never know for sure, but I really appreciate your input. Makes me feel better about NOT being able to figure out what these things were. Best, R.