6N2 Polo Gti air con tempremental

Hello, hopefully someone has had same issue.

  On way to work, got stuck in traffic, temp gauge went up to 110', got to work, bridged fan switch, fan didn't work either high or low setting, so ordered fan.

Fan works fine, but when I put air con on, does not engage, and low feed fan does not kick in, had a look on line, found out possible fan relay under battery, ordered this and fitted 9 although slightly different casing, was told it would fit, fitted after disconnecting battery. Put car back together, hey presto it worked....so I thought, after switching car off going back to it, switching air con nothing, scratched head looked at fuses(fine) disconnected battery and reconnected, started to work again.

  Went to start car today, air con again not engaging, disconnected battery nothing, left for two hours , started car, air con comes on. switched off then started again ....again no air con.

  can anyone help.

 Thanks  Alan