how to test a thermostat

Hi guys can anyone help me in understanding how to test a two pin chest type freezer thermostat .how to check cut in &out points etc.What ohmic value to expect.

Problem :The thermostat cuts of the freezer manually but when turn back on the compressor runs continually.:eek:

.

If the comp runs all the time the stat is faulty.
The fact that you can manualy turn it off and on just
means the mechanics in the thing work.

Best just to replace it.

taz

.

Also wise to check temps on freezer,running constantly it should be -24c or lower,sometimes the insulation deteriorates at the bottom of the freezer (although possibly not in your part of tjhe world),if there is any damp underneath or on the lower areas of the cabinet the insulation can be shot which will also cause it to run constantly,scrap then.
BG

Thermostat is only open or closed circuit.As said above, if freezer cannot reach temperature, than thermostat will stay closed and compressor will continue to run. If freezer air temp makes say, -20c, and stat will not switch off on minimal setting, then toss it.

try and putting in ice water and check for cutt out of compressor

Quote:

---

Originally Posted by shonal

try and putting in ice water and check for cutt out of compressor

---

Shonal,How's it going out there in paradise? A freezer thermostat is not going to cycle in iced water. Has to be much colder than that:).. mike.

What I normally do when faced with mechanical thermostat problems...

I have rigged a circuit (similar to a torch) which includes bulb,battery, and a modified switch with two extended leads which connect to the thermostat being tested. When there is continuity in the thermostat the bulb lights up.

I put the thermostat with its sensor in a working deepfreezer capable of a lower temperature then the thermostat requires. I include a digital termometer with a extended wire sensor in the freezer as a guide. Initially the light is on since the sensor is warm and there is continuity ... however depending on the dial, as the thermostat sensor goes colder to reach its envirnment temerature, it should cut out on its set point... since the freezer is colder then requirements, putting the light out.

Not very accurate but should serve the purpose of determining is the thermostat is working

Thanks guys with all the info ill tell you'll how things go with that .