I have 2 1997 f350's. One of them blows powerful out of the vents on max ac. The other one blows considerably less out of the vents. Both are cold temps though. Does anybody have an idea on what could be wrong with the weak blowing from one truck versus the other?

 

Nothing is wrong, it is designed that way. It blows harder on Max than on norm setting. Mine does the same thing.

It may be that the fan on the older one is getting plugged.


Maybe I need to read more thoroughy! It may be that the housing has some gunk in it on the weak one, or the motor may be getting tired on it.

 

hey! quit complaining......lol mine needs a kick start to get going!

 

Are you getting all 3 speeds from the fan? If not it may need a Heater Blower Motor Switch Resistor.
The HVAC system takes air from outside unless it's in the Max AC mode, then it takes air from inside the truck. The fan doesn't speed up it just moves more air due to less resrtiction. IF you are getting all 3 fan speeds then you may have a restriction in the MAX air intake. It's located at the passenegers feet. I've seen plastic bags get sucked up in there.

If there's no restriction the Air Inlet Duct Door isn't working. It's vacuum controlled. It's behind the glove box IIRC.

 

On edit. You can see the Vacuum Control Motor under the dash, it's located directly below the left corner of the glove box. It will move when you put it into Max AC.

 

thanks,,,, I will check this out after work tomorrow.