1999 E350 Super Duty van
 

A/C blower works on low to high but, slowly. One day it was fine blowing hard and next it was slow. New blower and resister. What needs to be checked next, any guidance would be appreciated. Thanks from hot AZ.

There were some problems with the blower motor speed control switch connections overheating , rusting and placing high resistance in the ground supply to the blower motor thereby reducing speed and function.
There were wiring kits available to correct this, and if the switch was overheated too much, best to replace it also.

Okay, 2 days and $647.58 later, my ac is back to blowing like if was. Switch, resistor, and blower motor replaced. The shop claimed it was blowing the best it was going to for an old van (108k mi). I said the van is old but, all the parts are new, now. Another full day of diagnosis and replacing a wiring harness and it’s back on the road.