First I'll start off by giving you all of the model and part numbers that I could find on my unit. I have a Carrier
Weathermaker 8000 Variable Speed 58UHV030-16 serial # XXXXX the control board is HK42FZ010, the Airflow Selector is CESO130028-00, the outdoor unit is a Carrier 38TXA048300.
The problem is a couple days ago the blower stopped working. I had a local Carrier repair tech come look at it and he replaced the ECM on the blower motor (the thermistor had burned off). Now the blower runs, but there is almost no airflow. Now when I say that "there is almost no airflow" I mean at either the return or the ceiling vents. (The return vent is one large vent directly below the platform that the unit sets on; all of the air vents are in the ceiling.) The problem persists even if I take the air filter out of the equation (out of the unit). I have also taken the cover off of the box on top that houses the air conditioner coils and they look clean and are free of ice. (The tech that came out seemed to think the lack of airflow was a blockage here; I disagree, if the blockage was here, that would explain the lack of airflow at the ceiling vents, but not at the return.) If I turn it on the larger pipe on the outside unit will get covered in ice; the tech thought that maybe I was low on refrigerant, but that checked out OK. Also, we tried the heat and that starts its cycle then kicks off due to a thermal protect (code 33). Although I didn't check at the time, I think the coils inside were probably freezing up (when the pipe outside was freezing). My thoughts are both the problem with the AC and the heat are attributed to a lack of airflow and my conclusion is that the blower is not spinning fast enough.
For me, this narrows it down to : a bad Control Board, a bad Airflow Selector, or a bad blower motor. Personally I think it's one of the two circuit boards, although I've examined both and don't see any burn marks on them.
I am pretty handy with electronics; I have a multimeter that I could do some tests with if I knew what (or where) to test. Also, I probably could have replaced the thermistor (I can do soldering) and saved about $400.
I guess the answer that I'm looking for is "where does the problem really lie?"
I don't want to waste a lot of money randomly switching out parts or doing unnecessary work (I'm sure my bill with the Tech is already over $500).
If the problem is with any of the above mentioned parts, I can replace any of those myself.
Any help you can provide would be great.