Cooling of my 383L+

[amenophis]

Hi everybody,
last week my 383L+ returns from Atik and there's the next problem 
It takes a long time to reach a temp difference of 15 °C.
I startet at 10 °C (outdoor) and set the temp on -5°
I reached -5 after 20 Minutes of cooling.
This can't be true, there must be something wrong.
Before I sent the Cam to TS (They sent it to Atik) the cooling works fine and muh faster.
I use a powersupply with 13.8V and 8 amps, that's defenitively enough (it worked fine with this settings)
Thanks a lot,
regards,

Thomas