Have a trouble with goodman furnace GMVC950704CX. Customer complain blower speed too slow when they use air conditoiner.I checked it ,the blower only run at low cooling speed. Flashing "C1" and "9". I adjusted #3 to off and #4 stay on of switch bank S3 ,so speed run up to "10". According to the manual, the high cooling stage shoud be 1600 rpm. Could you tell me how it can go to "C2".

Thank you