Unit 1, gas company shut off gas to unit stating it was putting on carbon monoxide and gas into space. Upon further determination found inducer motor not performing correctly which is what might have caused the heat exchanger to get to hot and crack. Unit will not even close pressure switch to attempt to run. Unit (200807-AMGF43728). Recommend replacing all heating elements ( heat exchanger and combustion motor assembly or unit replacement as it is 12 years old and normal life is 15 years of package units. Spoke with Chad and Lisa both are interested in repair and replacement cost and time frame of unit. I have attempted to call Aaon themselves and left a voicemail to get pricing info and a distributor, both I am waiting to here back from on parts pricing and availability. I have been told they are a minimum few weeks out on parts. Commercial replacement form completed and sent for estimating. Customer has been sent a quote for repair, parts will take 2 to 3 weeks to arrive.