Coca Cola Drinks fridge thermostat.

Today I went to a Coca Cola drinks display fridge.
It stands about 5′ tall and has a glass door. It has a switchable illumination at the top.
Inside there is a fan visible towards the top on the back wall.
My customer has this in his garage. He told me that he has fitted 2 thermostats himself and he cant get it to work properly as it just freezes up inside.
When I looked at it, he had just pushed the capillary tube up behind the metal back plate and into the fins on the evaporator. He told me that he couldn’t remember where it originally was 🙁
After looking closer, I noticed a metal tube like part of the evaporator with a bell bottom. It seems the perfect width to accommodate the capillary tube. I’m assuming he is trying to run this with a VT9 universal thermostat so I know the contact temperature wont be correct. Perhaps if anyone has been to one of these before, some help could be passed across please?
Thank you,
Rob.