Beer temp swings

I have an ale that is fermenting. I am looking at the graph and noticed some large swings in beer temp. It is supposed to be at 68F and as soon as the fridge kicks on it drops the temp too much. now the heater has to run for hours to get from 65F back up to 68F. Then it will cool and drop too much again. Please help me figure out what’s going on or what settings to adjust. I can post additional info, just let me know what you need.

First of all, awesome beer name.

Second: do you have the beer sensor inside the beer? Your beer temperature seems to move very much the same as the fridge temperature. Do you have it taped to the side? This won’t work well. Definitely not with the Arduino version.

Also, try moving your fridge sensor closer to the back of the fridge so you will have less overshoot. Try moving the beer away from the back of the fridge, so the air temperature cools the beer and not the fridge directly.

Hi, thanks for the reply and all of the work you have done!

I have a thermowell in the fermentor and the fridge sensor is in a jar of water at the back of the fridge. Should it be sitting out in the open air? You can see the thermowell in this pic. the fridge sensor is in the jar to the back left. the jar on the front right is for the blow off tube.

You can see what the brew is up to here:

also, this last round of heating looks like something is wrong on the graph. That’s because my paint can heater had the light burn out. I swapped bulbs and it is back to supplying heat.

Yes, please try with the fridge sensor just in the air. Also see if you can push the beer thermowell as far down as possible and make sure the sensor is all the way down the thermowell.