Anybody knows about refrigerators and freezers?

[e9999]

All right, so I got myself an almost new free minifreezer (120V AC) on CL that I plan to try to use for my truck or camping. Of course, it doesn't work...

Took me 5 mins to figure out that the thermostat was the culprit . I bypassed it and it's cranking out fine. It's now down to 7F after about 1 hr or so, so not too shabby.

Anyway, I gotta fix this thermostat cuz I don't think I want it to run full time.
I will call the company next week and see if they have parts for this.

In the meantime I wanted to know a bit more about it.

Could somebody who knows about these things have a look at the 2 pics showing (not very well, sorry) the thermostat system and tell me whether it's likely that the thermostat electromechanical box and the sensor tube have to be replaced as a unit or whether you can take off the tube. The latter would be better to work on it and it looks like the sensor/bulb is buried in expanding foam insulation. Tube looks soldered on box, though, so not promising.
Also, are there some common malfunction cases that cause problems with this kind of thermostat?

Here are the pics:

 

[e9999]

second question:
what are all these refrigerant lines doing?

I can see a hot and a cold coming out of the compressor (B and A). Ok, that's obvious enough. The C gizmo must be the orifice to drop the pressure, no? But why is it joined with A (or are they just in parallel under the insulation) and going its separate way into the freezer inside on the thicker side? Are the condensor and evaporator not directly in series? What's the general layout here?

 

[e9999]

well, I took the thermostat apart. It's one of those funky electrothermomechanical switches with lots of pieces fitted together, rotating over fulcrums with stops, springs etc, the kind that's kinda like a lego set... I had one of those on the pressure switch on my compressor which I also took apart and could not put back together... you'd need 5 hands or some gigs...
Fortunately, this one I could put back together . Has some minor adjustments but it didn't flip as needed at reasonable temperatures. I'm thinking there is something wrong with the bulb, tube, or diaphragm (the latter being the gizmo that contracts and make the switch flip). I was able to take the diaphragm off when taking the thermostat apart. Doing some tests now.

Of course, I could possibly be able to buy a new Tstat assembly but eh not as much fun that way...

So, anybody knows if these bulb gizmos go bad easily? Could it be simply that it is kinked too much?

 

[e9999]

well, took the bulb/tube/diaphragm gizmo out. Doesn't look like it's doing anything. No change in diaphragm length over the range of -20 to 200 F or so...

must have been leaking and is now empty.

What's in these things anyway?



oh, and you fridge experts out there, don't reply all at the same time...

 

[Bogo]

Generally you will have to replace the whole thing.

There are 12VDC powered electronic versions you could replace it with.

Controls & Electrical Components

 

[e9999]

Generally you will have to replace the whole thing.

There are 12VDC powered electronic versions you could replace it with.

Controls & Electrical Components

thanks
it's 120V unfortunately.
But I got the manufacturer to send me a new thermostat, I hope.
Man, that thing is going down to -20F in no time at all...
Now to see if it will work in the truck when going up and downhill...
mmm.... about 70W when running at steady state temperature, about 6A at 12V plus converter losses.... not too bad. Bit more at startup of course.

 

[e9999]

Fixed!

 

[e9999]

Yo 88!
do these pics tell you any more about what I have? Is that a capacitor showing in pic 2 of post 2? The one with the brown 90o connector?

 

[knoll0351]

I am by no means an electrical expert, but I don't see a capasitor in any of those pictures. Would look like...a soda can...but much smaller for use on something like this...

 

[herpestes]

same operation theory as your auto ac. on a unit that small there is not capacitor thus you most wait awhile if unit is unplugged or shut off before restarting. reason for this is that the compressor motor doe not have high starting torque and most wait for the gas pressure to equalize between the high and low side of the system. there is a relay and overload under the cover on the terminal connection on the body of the compressor. the problem with the thermostat is that it most likely has loss its gas charge in the sensing tube.