I have high efficiency carrier. It has the large black wire on the cooling part which I understand is the fastest blower speed for cooling however it doesn't blow fats at all it's very slow. I tried the red and yellow wires and it was the same speed. What else do I have to do to get the mirror to speed up?
I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.