How do I get my heater to blow thru the vents in the dash and the de-froster? All the air in the truck only blows thru the floor vents?
The most common problem I've heard is that (for defroster vents) there is a flap inside the ducts that breaks so it will not divert air to the defrost vents. This does require removing the inner ducts. You might also want to check the vaccuum hoses and actuaters that divert the air to the different vents. If you'd like some pics of what I'm talking about I can try to post them up, I currently have all the compenents in my room (trying to convert my truck to a/c by next summer :7 ).
This pic is the main inner ducting/heater core box as you would see it installed in the truck (floor = firewall). The white arrow is the small part that commonly breaks. This one is broken, but there is an unbroken one sitting to the right. It has a tab on one end for a screw. The red arrow is the flap that allows air into the dash vents (its actuator is on the other side against the firewall), and the green arrow is the floor vent. The blue arrows are the defrost controls. The vaccuum actuator is on the driver's side of the ducting, and pulls the flap at the top (other blue arrow) down to allow hot air up through the defrost vents. If there is a vaccuum leak on either of the actuators or if they have gone bad, the flaps for the vents and the defroster wont open. Unfortunately, I think the only way to test if they have gone bad is to pull out the entire box (which requires disconnecting the heater core). So the first thing to look at are the vaccuum lines leading out the back of your heater controls, and the lines in the engine compartment. Look for your vac booster (a large plastic ball on the firewall with 1 or 2 vac lines coming from it), one line should run to either your carb or manifold, the other should run into the firewall. If any of them have been disconnected or are loose, cut, or cracked; they are most likely the source of your problem.
