Has anyone had issues with the volume of air coming out the dash vents when the ac is on. my 90 2500's ac is ice cold. when the fan is on high it has normal air flow after a while the airflow decreases. it will not increase untill the truck is turned off then restarted ac on fan on high.although this does not always work. does anyone know how many blend doors and dirverter doors and controlers there are for a truck with electronic hvac controls. my controls are not acuated by cables and i do not have max or recirculate switches just ac on and off. my fan motor is new. thanks for any help.