mack granite hvac no air flow please help!

[mikey3131]

im hoping someone can help me I have a 2005 mack cv713 granite im getting very little air flow from hvac unit with blower motor on high air just barley comes out. now I have cleaned blue cab filter also checked blower motor for missing fins and dirt and it works great, with black plastic cover off the blower motor it sucks in air from cab and I get my air flow from the vents back. but with cover back on blower motor I lose air flow again.....im hoping someone can help me out any input would be great thanks..

[rsb502]

sounds like the evaporator and heater core are stopped up pretty bad, I had this issue whe I bought my 2004 Granite, the guy that drove it before i bought it kept the AC on low so it was pulling in outside air at all times he never turned it off or put it on recirculate. The big issue there is that the Granite pulls its air in from the bottom of the windshield and the dust durin a days time rolls down the windshield and gets sucked right in the A/C, I took the heater core and evaporator out and you could barely see thru them, I cleaned them out, cleaned the box, put a new dryer in and charged the system, it was like night and day. I was having trouble keeping it under 85 degrees in there in the summer, after I did the clean out I had to keep it turned down or open a window it would freeze you out even when it was 90 outside.

[rsb502]

the cab fresh filter company makes filters that go over the air intakes outside on the cowl, they help a lot I got em installed during my clean out and I actually have always tried to keep my dump trucks on low and recurculate in dusty areas because of the dirty air issue, if your driving thru dust, your sucking it into the AC and its sticking to the wet evaporator guaranteed.

[mikey3131]

thanks superdog im gonna try cleaning them out, I think your right the truck spent most of the summer hauling on site,lots of dust..

thanks for all your help

mikey

[krismoriah]

There is a flap under the dash that opens and closes..if its stuck shut you wont get any air thru the vents..I think it runs on a cable.. If this is the cause of you not getting the airflow you need then you can manually open the flap and put a self tapper screw to keep it open until you get the correct parts to fix. You may have to roll down the windows if it gets too cold, but at least you will have cold air coming thru the vents. Its been awhile since i did it but its not hard to do. This was a fix on a 2005 granite CV713 of mine due to no air coming out of the vents. May or not be your problem.

[turckster]

Before you try to pull out the evaporator and heater core, make sure that you can change vent direction--defrost. floor and center. If its hard to change vent direction or it is stuck, might as well prepare to change the mode box. The hvac unit has to be removed completely in order to change the mode box. While its out the evap. and heater core are much easier to remove. If it all works ok, then what 84superdog said would fix you up.

[bbigrig]

Pull the cover off the heater/AC unit and dismount the actuators for the vent doors. if you move them manually and you feel a difference Bingo! like the boys above have said. Cheapest fix.