Well I still can't since he came, looked confirmed that it IS the heat exchanger, and called to check availability, now I am waiting for him to cal me back to see if a heat exchanger is available for my model or if the entire unit has to be replaced. but he removed the blower fan and I saw the hole, after running it as long as we did before I suspected an hole and the Co detector not blaring, I'm surprised were alive, the Co level in here was 17 ppm the day I checkedNow now, let him give you the estimate, THEN strangle him. You must THINK.