The thermostat is dead in my strange¹ fridge with no replacement parts. I posted about the mystery component before.
There is a metal plate that appears to sandwich a single small loop of refrigerant (guessing!). Mounted attached to the backside is a coil with a ground and two wires marked to handle 220v. One of the leads connects to the LOAD wire on house mains and the other to the (now broken) thermostat.
I can only imagine that it’s a heating element for defrosting (as suggested). But I struggle a bit with that theory because I’m surprised the fridge would ever get cold enough to justify defrosting.
Anyway, I wired the mystery coil directly to mains and left it for 10 min or so. The temp of the metal plate did not feel any different. Is that expected? Metal is naturally cold at room temp and that did not change.
I would like to understand it because I cannabalised a simpler t-stat from another fridge. The t-stat has no connector for whatever the mystery component is.. it’s just a switch that connects two wires. I don’t know if I should just omit the mystery component, or if I should wire it in series with the new t-stat, or keep it attached to the old broken t-stat and wire that in parallel to the new t-stat.
¹ I say strange because there is no freezer-fridge vent. So the fridge is independently cooled.
I posted a pic in a reply but the component is hidden behind the metal plate.
I wonder if it is a thermal fuse, then I don’t know what would warm the plate. It has a coil of refrigerant which you can see in the pic.. just one loop of coolant. I’m baffled that it’s enough to cool the whole fridge compartment. As far as getting warm, I wonder if the compressor could somehow run in reverse and push hot refrigerant through the coil to defrost things?
I've seen the pic. So the plate is not the component? I thought the whole plate was the component. In that case, if it is a small metal plate like any of this, then it most likely is a thermal cutoff.
It's not running the compressor in reverse necessarily. It just used to sense when the temperature of some point has reached some threshold. Remember, a high temperature on the cold side could also be used to trigger the compressor to cool down the fridge.
The mystery component is hiding behind the plate. If I follow the two white wires from the thermostat, they go behind the plate and make a loop that attaches to the backside of the plate.
I mean, you could also say the plate is a mystery to me as well. I’m quite baffled by this fridge because it’s nothing like the videos I’ve seen on fridges. The plate must be cooling the fridge compartment because there is no vent coming from the freezer.
I should mention that the /load/ wire that the mystery component connects to is the /return/ load going to the compressor. But that connection jumps to the t-stat. So I think it cannot be a cut-off because it’s wired in parallel to the compressor’s load input.
So from how it’s wired, I think it’s expected to be a heating element. But it’s not warming the plate when hotwired. So maybe is a broken heating element.. but yet it has continuity (14.15 kΩ). So I am baffled for sure.
I guess I can only hope that someone has seen this bizarre Zanussi/AEG design before.
Yeah, that's a broken heater. A broken heater sign is usually high resistance or good ol disconnect. It being in parallel further reinforces that. This is a common schematic for domestic refrigerators.
For the moment I just disconnected the heating element and wired in a t-stat from a mini fridge. The heatin element could very well have been broken as long as I owned the fridge (it was given to me as a quite old 2nd hand fridge).
I guess I will keep my eye out for similar normal sized fridges that are trashed. Maybe I can harvest a heating element and combined t-stat like mine to recover the auto-defrosting function.