Got this 1984 Ford Van 113,000 miles with a heavy suspension and towing package pulled by a 460. When I got it, the heater blower motor was siezed. I replaced the blower motor with a new one and it spins up and runs like crazy, problem is there is very little air flow out of the vents. I move the selector to floor, mix and defrost the air comes out the different places but very little of it. The air is very hot, just not much flow. I see nothing disconnected under the dash and can't understand why so little air flow. Van was owned by 1 family since new and I asked the former owner about it. He tells me ever since the van was new it was like that. They used to put a curtain behind the front seats to trap the warn air there as there was so little of it. Any idea on a fix for this problem?