Volvo Repair: Bad luck..., cylinder head work, air control valve

Question
I have a 1998 Volvo S70 2.4L non-turbo. I bought the car last October without a warranty and low and behold two months later the idler pulley on the timing belt seized up and I fried 19 of 20 valves at 107,000 miles. The car sat for 10 months until just two weeks ago I replaced the engine with one with 50,000 some odd miles and now my A/C compressor which was kicking on and off every 10 seconds will not engage. I bypassed the relay with a paper-clip and it works again, however, once the compressor runs long enough the freon starts blowing out from somewhere. Before this happens the air does get cold. Am I lucky enough only to need a new relay? Or this something else? Oh and also my Idle Air Control Valve code under the service engine light is coming up, is there a reason to spend the $452 for name brand at Murray's or is a $140 Volvo OEM just as good? Thank you very much!

Answer
Ryan, unless you got a good deal on that engine, it wasnt necessary to replace it.  Valves and cylinder head work would have saved you money.  You may need a pressure switch but then again, the evporators on these are known for leakage.  Idle control valve code?  or air pump code?  havent seen too many Idle valve codes on these.  Volvo OEM is best.  You never know what you are getting with aftermarket junk.  Roger