STC preventing fridge from cooling

[TSMill]

I had an issue with my keg fridge a couple of days ago, noticed the temperature was creeping up above my setpoint (3.8C), got as high as about 6 before I shut the whole thing down. Note, the STC has been in operation for ~ 6 months with no issues, and in addition the fridge thermostat is also buggered, basically without an external controller it would drop below freezing.

Whilst the temperature was rising, the STC was definitely providing an output to the fridge, the compressor was running non-stop and the rear of the fridge was getting quite cold. The cooling coil inside the fridge was cold, but not as cold as it should have been.

I've tried the fridge this morning, both via the STC, and directly via the power point. It's definitely providing more cooling output when the STC is not being used. Is it possible that the STC is providing some sort of resistance, such that the compressor motor is not getting enough juice to operate effectively?

 

[Ducatiboy stu]

STC shouldnt affect the amount of power to the compressor, but saying that your symptoms suggest otherwise. I am not sure if the STC provides a relay contact type output.

Does your fridge have a fan in the back somewhere hidden. If it does, make sure it is working as it is essential in circulating the cold air from the condenser pipes.

 

[TSMill]

There is no fan, the cooling coil is at the top of the fridge, cold air should drop to the bottom.

Like you suggest, I would not expect the STC to result in a voltage drop. My first instinct was that the fridge was out of gas, but running it with the STC bypassed (but still measuring temperature) I was getting down to -2C measured, whereas when running via the STC its getting to ~7C with the compressor running non stop.

 

[Ducatiboy stu]

Has the position of the STC probe changed ?

 

[TSMill]

Nope, probe usually sits in a ~200mL bottle of water to provide some thermal mass. Other than the temperature reading though, I can tell by touching the cooling coil that it is not cold enough with the compressor running flat out.

 

[Ducatiboy stu]

Does the fridge motor feel warmer or colder when run using the stc.

 

[Camo6]

Could you plug a lamp into the STC output and then into a GPO and compare brightness? Or maybe a fan or such.

 

[TSMill]

Definitely was quite hot when running flat chat a few days ago, assumed I was just out of gas.

 

[TSMill]

Nice idea, I'll give a fan/lamp a go.

 

[Amber Fluid]

What are the settings on your STC?

Do you have your fridge turned on for the coldest temp?

 

[TSMill]

OK crisis seems to be over. I pulled the STC apart and one of the connections on the cooling circuit was loose (pulled out by hand). Tightened it up and everything seems to be working fine. Strange, I would have wired it up over 12 months ago and has been in a sealed container, never missed a beat until now.

 

[Ducatiboy stu]

Sometimes it doesnt take much vibration over time to loosen a conection

 

[TSMill]

Yep, its an old fridge (picked up off the side of the road about 3 years ago), so natural reaction was that it was out of gas, lucky I gave it a test run without the STC before it ended up back on the street.

 

[Camo6]

Sometimes it doesnt take much vibration over time to loosen a conection

TWSS

 

[Ducatiboy stu]

Even if she was old and frigid