Ok here's the story, last week I got a no heat call at a local strip mall. Went onto the roof to check the unit. Off on flame roll out. Reset and unit started up. Check the heat exchanger and find 2 cracks, about 30 inches long each. Red tag unit, notify owner, shut down gas, electricity, disconnect w on stat and shut down the gas valve. Office quoted replacement and everybody went on their merry way. Happened to be on the roof again today (separate unit) and happened to notice on of our competitors working on the unit I had shut down. Figured we had lost the bid, no biggie at this point. Run to the supply house and come back fix the unit I was working on today. Look over and see that my "friends" have left. My mind says "weren't here long...I wonder?" Quick look over shows that they cut my red tag off and restarted the unit without fixing anything. Speed dial the service manager (who i e-mailed pics to immediately, aren't smart phones great!) and bring him up to date. He tells me to go talk to the guy who owns the unit. Long story short brought the guy onto the roof, showed him the very visible cracks as well as the fire (visible through cracks on run cycle). He says "well the other guy put a meter in the duct and said we were ok only 20ppm." Explain to him that the heat exchanger has failed and needs to be replaced. He asks if he can confirm this with the service manager, phone call fixes that. Asks for another tech to come look, had a guy nearby who swung over and confirmed my diagnosis. This guy then has the balls to tell me that he has the guy who ok'd it on his way over to confirm the failure! I tell him I'll be waiting. 1/2 hr later (5 degrees and windy) he says "oh he'll be here in the morning . Re-red tagged the unit and this time I put my lock on the disconnect. I just can't believe this.