Sounds like premature bypassing as the highlimit switch would cut off fan and compressor. If it has been running high head pressures for a while due to dirty coil or overcharge (although not high enough to cycle limit) it could have casused premature failure. The Tech can diagnose for sure. Better that it is r410 than r22 price wise though it may not be contaminated. Have you had any problems with the contractor that installed it? *some* are easier on recent systems they installed, but if its big money dont feel bad about getting quotes.