Mechanic who changed out AC compressor says Harmonic Balancer appears loose - moves a little - as though serpentine belt caused rubber to give a little when the AC compressor froze up... Should the harmonic balancer have ANY play in it? What has to be taken off this '94 Suburban to get at harmonic balancer to replace it?  

first, the ac compressor locking up did not put enough of a strain on the belt to cause the problem. secondly, harmonic balancer failure is not unheard of. the rubber in the balancer is a known failure point on any engine that uses, especially on the diesel due to the nature of more internal vibrations. you can replace it with a stock, new piece, but would reccommend an aftermarket piece. heath diesel and 65dieseldirect.com are both good sources for this part