A new motor fan and control card has been installed in my Rheem Criterion II. The blower speed is much too low in all three modes (fan on, heat and cool). The contractor who did the repair tried many different settings in many different scenarios (Hi, Med High, Med Low, Low). High and medium high are barely there and low is almost no flow at all. The person doing the work was baffled. The contractor is coming back next week to try again to resolve the issue.
I want to be "literate" in this particular problem so that I can evaluate if the contractor is doing the right things to resolve the problem. If not, I'll have to go with someone else. In that case, I'd want to ask the right questions of the new candidate to know if they have any better chance of success.
I think I understand how things work pretty well. You would want to test if the right voltage is being supplied to the motor, you would want to check the run capacitor with the right diagnostic tool. Failing finding a root cause in either of those two things, what would be the logical next steps after that?