Fermentation Fridge not cooling

[PintOfPlain]

Hi guys
hope you can advise me
I bought a large second hand coca cola fridge
I can double stack two 5 Gallon fermenters

I use a johnson digital controller
I have the probe in 1L of water, set to 68F with differential of 2F and 12 minutes cycling

When it first comes on , the fridge cools great, cools right down quick and then cuts off as it should

the problem is then with the second cycle - when it comes on again, the fridge seems to enter into some sort of "circulation" fan air mode, without activating the cooling.

Not sure if its the fridge or the controller problem. I think the fridge.

Thanks for any tips!

 

[day_trippr]

Remove the Johnson and see how the fridge behaves on its own...

Cheers!

 

[beaksnbeer]

Try changing differential to 5F what you may be having a high head pressure start problem. I let the temp. probe at air temp but set to 62*-63* which holds active fermenting wort at about 66* in my fridge temps vary by location, insulation, etc.
I tweaked mine in with a temp probe in the fermenter, after primary I bump the temp to 68* and the beer will hold that temp without more then 1-2 degree fluctuations.