PLEASE HELP AC PROBLEM FABIA 1.4 TDI

2008 Fabia 1.4 TDI. Recently replaced the radiator and AC condenser and fan assembly due to a crash. Everything worked fine until the AC main pipe plastic link lock burst away (right below the coolant cane) due fan not functioning replaced a new fan. Then the AC main pipe had to be replaced but due to non availability the plastic lock link was altered and replaced by cutting away the locks on both ends and threaded on both ends with Teflon and replaced with a copper link coupler. There was no leak of gas now when checked with a pressure gauge.

AC was working fine but within a day again it did not work, the AC current supply was there but the compressor fails to switch on. When the gas was released I noticed black oil coming out. And immediately dismantled complete AC unite apart and cleaned the entire system independently with thinner/petrol, air cleaned, dried and refitted and also replaced the condenser along with dryer and replaced a refurbished AC compressor and it was working fine again within a day the second compressor failed. Ac power supply was there but compressor doesn’t switch on and when gas was released it was fine. Now without choice I had replaced brand new compressor OE it was also working fine and within a day had failed again WHAT COULD HAVE POSSIBELY GONE WRONG PL ADVICE.

AC COMP model

VW AG 6Q0 820 808D /GE 6SEU 14c TDI/ 2008 05 32736/ Ge44719-8895/ R134a/ Denso

the system is semi automatic air con system with 3 control knobs