On Heat mode, when blower motor comes on, cool air comes out of the registers and fan is noisy. I think the hi speed comes on instead of the low speed. there are three wires going to the blower motor, Red, White and black. All are connected to the terminal which are marked R W B correctly. Can anyone tell me how to correct this problem? Furnace is a Coleman reverse flow 5600 BTU DGAA 070BDTA Serial No.001115253
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