Volvo: 1986 240 DL AC, freon, fuses

Question
Recently chraged the A/C system and there is  no loss of freon.

The A/C sometimes works and sometimes not.  I play with the A/C knob and turn it off/on and try my luck for getting the A/C on.  when it works it is cold.

Is this related to an A/C Relay problem?  how can I change the relay / location of the relay.

Thank you

Answer
MK,
Make sure that no power is at the clutch when A/C goes out. Then see if all fuses are good. The relay is in the center control panel on the right side below the switch. Make sure the switch has power. I have seen the wires under the hood fray and break, look all them over also.