lack of defrost

[IAN_M715]

guys my truck will not defrost. ever. i have the blower motor switch on, the heater cable pulled all the way out and still nothing, no hose blockage that i know of, no disconnections and i get no air pressure across the windshield. about 45 minutes into the ride, my passenger side develops a nice portal to look through. ummmm what happened? what'd i miss?

[stanman]

Is there any air coming out of the ducting?

[rjenkins]

if the fan is running look for air at other points. If no air at all look for a cloged heater core (mouse nest)

[brute4c]

The stock defrosters blow very flat to the windshield only right above the openings which are partially restricted due to being recessed down in the windshield frame a bit. I have issues with defroster output when its really cold...below 0 and down...

Did you verify that the cable is fully moving the arm and that the plate inside the underdash box is fully moving from heat to defrost?

First, do you get heat? Maybe its closed off some at the heater core and you arent getting any heated air coming in....the blend air door in the underhood box would be the one to check there...make sure it is being fully opened.

Remember, just because the cable moves the arm on the outside of the unit does not mean that the door is opening and closing on the inside...or that it is moving through its full range...need to verify if it is truly doing what it is supposed to.


Also, it is possible that the fresh air intake is plugged...if you stand on the passenger side of the truck, the grill work on top, just behind the windshield, the cowl, is where the fresh air heater breathes in from. Leaves and debris can get in there and then get sucked into the opening to the fan thus restricting or completely blocking off airflow.

[IAN_M715]

will check all these points. no air is moving within the cab.

[brute4c]

Let us know what you find....no air movement means something is wrong...