At my wits end, cant get air flow out vents and no one setting is better than the other, 99 f250 SD v10 xlt, going back 2 years or better to when it worked last, I noticed it had vacuum leak and when accelerating it would change from dash to somewhere else while wanting max ac, I let it sit a fair part of winter and had addressed some of my vacuum leak issue, the hubs were changed to manual locking and vac lines not capped, so that fixed that, that winter while sitting, I had some rodent issue and was thinking they nested in somewhere, I had weaker flow but not terrible and also got noisy fan motor around same time, attributed the issue to the fan motor going out, new fan motor and still weak flow, the old clocked out completely, new squirrel cage was rubbing and broke so I had to also put that on new, verified voltage to be good at motor on high, and other speeds step down right, now its sat since fall with a blown plug and critters moved in again, had blower motor out and cover off evap tonight, the evap doesnt seem bad at all, I blew it out with a radiator 90 degree blower, and shining from fan side on what I could on lower side I could see great light, blend door is moving, manually vacuumed and checked all but whatever the red hose goes to, that heads towards center of truck behind plentum, what I can see of it is in tact, the double hose connection, blue and yellow??, was holding vacuum when I took it off its actuator and truck had sat over an hour, I had cover off and blew heater core out last year, I cant get any air out defrost and my face vents dont get any air to my face or enough to feel hardly, I placed a piece of towel in front of evap when I had cover opened and the towel showed air flow, I dont have experience in how much is enough, but i was trying to made sure it wasnt sucking up to the evap, so having said all that, I'm hoping to get a few pointers on what i need to do to test or track down my problem

 

After searching and making sure all was clean and nothing plugged, all doors worked, and evap and heater core were clean, I figured it out, I pulled fan motor, ran it with vehicle plug and observed rotation, put in vice and ran both directions with jumpers, it moved more air the other way, unpinned the vehicle plug and swapped the wires and problem solved, think the supplier has the internal leads hooked up wrong inside motor, anyways shed working again and I'm happy to have figured it out

 

Son of a gun! That motor sucked instead of blowing!