Refrigerator compressor will not stay on

I’m having issues setting up my brand new brewpi spark to control the refrigerator compressor. The spark, sensors, and web interface all seem to be working normally, but the compressor will not stay on to cool the fridge. Please see below for pictures of my setup.

I followed the fridge hacking guide first under Method #1 (switched power cord) and later with Method #3 (fully integrated SSR) with the same result. The compressor turns on for only a couple seconds at a time despite the brewpi remaing in in “cooling” mode (fridge constant 40°F) and the SSR having a solid red light. After a few minutes being off, the compressor makes an audible “click” noise and turns on again–only for a couple seconds and the cycle repeats. This also happens with the brewpi in Test mode.

Reading through other internet articles, I suspect this might be related to an interaction between my SSR and the compressor overload protector. The fridge seems to operate just fine on its own when not connected through the brewpi switched power cord.

Any advice on how to test my setup and wiring would be appreciated!

Refrigerator wiring diagram:

SSR switch box:

That SSR connection looks fine. You should but the SSR in place of the thermostat.

Other than that, I have no idea why this is happening, sorry!

Yes, I was able to put the SSR in place of the thermostat with no luck. However, I was able to get the system working correctly with another relay method:

Based upon this, I’m fairly confident a faulty SSR is the root of the problem. I have ordered a new SSR from the brewpi store and will update the thread if it solves the problem.


I wanted to update this post after resolving the issue. After swapping the existing SSR with the new on from the brewpi store, the system seems to be working as expected.

I know this is a bit of an old thread but i thought I would chip in in case someone finds this useful…

I had exactly the same issue as jgoings. Compressor stayed on for a couple of seconds and then went off. I also have a heater which works absolutely with no issues. I did purchase both ssd relays from brewpi webstore. The heater ssd is rated to 10a and fridge ssd is rated to 40a. As soon as i switched fridge ssd to 10a ssd the compressor has started working absolutely fine. Maybe the 40a relay doesn’t see enough load and switches off, i am not sure, but swapping the 40a relay for a 10a relay has sorted my problem.
With a quick search from jgoings picture it also seems like he was using a 40a relay…