STC 1000 Won't Stop Heating?

[Xwingace]

Good evening everyone!
I have a mini fridge wired up with an STC 1000 temperature controller. It works just fine for a month, but now seemingly at random the heating circuit just stays on. My heating element is quite simple, just 100 W lightbulb inside the mini fridge which works fine.
I've checked the wiring and that seems fine. Has anyone else experienced this kind of problem? I am going to try reprogramming the temperature limits again and see if that helps.
Just wondering if anyone else has seen this sort of thing before and if I'm missing something obvious.

 

[d3track]

Is the sensor properly connected as well as the heating cooling?

 

[Xwingace]

yes, that's how I noticed - woke up in the morning and it was at 43 C

 

[d3track]

Unless the setting was messed with, I can't think any other obvious issues

 

[Thetonymartin]

Are the the heat and cold hard wired, or plugged into an outlet? Check that a wire hasn't bridged the gap between the "hot" and "cold" side of the outlet. That could cause the heat to stay on.

But then again, the cold side would stay on, too.

 

[augiedoggy]

The relay also could have stuck on in the stc.... this usually happens more often when something with a higher amp draw than the contacts are rated for is plugged into it (100w bulb shouldnt do it) or the settings have been changed to allow the relay to switch without the delay to protect the contacts from overheating and fusing.... There is normally a delay of about 2 minutes I think set by default to protect the contacts as well as compressor motors of fridges.. did you possibly change this?

 

[Xwingace]

Switched it out for a 60 watt bulb, everything's good now. Thanks Augie!

 

[pcqypcqy]

The relay also could have stuck on in the stc.... this usually happens more often when something with a higher amp draw than the contacts are rated for is plugged into it (100w bulb should do it) or the settings have been changed to allow the relay to switch without the delay to protect the contacts from overheating and fusing.... There is normally a delay of about 2 minutes I think set by default to protect the contacts as well as compressor motors of fridges.. did you possibly change this?

Sorry if I'm misinterpreting: Are you saying that a 100w bulb will exceed the allowed amperage? I thought these things can take 10 amps as standard, and the fridge is much more power hungry than a 100w bulb?

Xwingace - where does the probe sit, is it in water? I've heard people say that water is fine for these things, and I was doing this myself until recently, but I noticed one of my probes has gone haywire and won't read anything accurately. Judging from the numbers, it's ALMOST possible that somehow it's switched from celcius to farenheit, but it's still a few degrees off. Mine was on the cooling side so things in my fridge got a bit frosty before I noticed.

 

[augiedoggy]

Sorry if I'm misinterpreting: Are you saying that a 100w bulb will exceed the allowed amperage? I thought these things can take 10 amps as standard, and the fridge is much more power hungry than a 100w bulb?

Xwingace - where does the probe sit, is it in water? I've heard people say that water is fine for these things, and I was doing this myself until recently, but I noticed one of my probes has gone haywire and won't read anything accurately. Judging from the numbers, it's ALMOST possible that somehow it's switched from celcius to farenheit, but it's still a few degrees off. Mine was on the cooling side so things in my fridge got a bit frosty before I noticed.

I meant to type "a 100w bulb shouldn't do it" its no where near the 10a max draw of the relay. Hopefully the relay contacts arent burned. sometimes a smaller load will still work for a while when this starts to happen..

 

[Xwingace]

Lol, well it's fixed it for the short term. I'll pull it apart this weekend and see what's going on inside.