I have a 99 f350 psd, i fixed the air gap problem and i also did the heater core bypass, but i just don't seem to be getting enough air flow. I put it in max and it seems pretty weak, could it be the blower or something else? It has always been weak since i bought it 4 yrs ago, thanks you all for all the help so far.

 

I'd suggest going by a car lot that has a Super Duty of about the age of yours and try the blower motor in it...compare the output to yours. Putting the blower on MAX only causes the blower to recirculate the air in your cab, rather than bring in outside air...it won't increase the amount of air being circulated...the blower speed only controls that.

 

May want to make sure the blend doors are working properly also ,,If heard of things falling from the glove box on some veh,, (like a pen or pencil) ,,blocking full movement ...

 

I know mine does not have one, but I have heard of a IN CAB air filter. Others on here have mentioned sucking up something from one of the air ducts, I ma just not sure where. Try doing a search, I would have no time at the moment

 

Had same problem with mine a while back finally had to replace the coils underdash because they were so pluged with dirt, and hair(from dog). Or you could just have something sucked up in there plastic bag, etc.

 

I took the vents off and put a leaf blower and all the vents where clear. maybe its a vent that doesnt open all the way. i also took the blower off and put the leaf blower in there also. maybe the blower fan is weak or it's my switch? i have no clue

 

Like mentioned already, a plastic bag sucked into the return vent is sort of common and will cause the problems you are having. Have a look of feel in the return vent for some obstruction, it will not be real easy to see or get to.

 

Where is the return vent located.

 

That's EXACTLY what had happened to mine. Someone here on FTE suggested to simply reach up under the glove box and see.

I did, found a flimsy plastic bag, and have had great air flow ever since!

It's worth at least a look...

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