hvac is gonna be the death of me

[novassracer12]

ok so I pulled the dash all apart and removed heater/ac box out. scrubbed everything down and put back together sealing every joint. I installed a 94 truck fan motor, new relay, new fan switch, new resister, new evaporator, new heater core. all the doors open and close properly. my question now is why is it when I turn my settings to heater the air flow decreases from te dash vents and comes out the floor vents? te only time I can keep full air flow to the vent is if I leave it on ac and the temp 3/4 over to full hot.

 

[Boone83K10]

You sound like me. My truck would blow hard out the vents on cold but very weak on heat. Check the seal and gasket on the vent distributor. It's the piece that attaches to the front behind glove box.

 

[novassracer12]

that piece was the one that fit the worst.when installed it had about a 1/2 inch gap between the box and it. I use foil hvac tape to cover it. I have triple checked vacuum line based off another thread here. very frustrating

 

[Boone83K10]

How about the gasket around the top of it? There should be foam that helps it seal to the vent T.

 

[novassracer12]

I installed it back with foam tape. it made a really nice fit then wrapped it with foil hvac tape.everywhere it had a seam it was sealed with the tape right down to the long seams on the defroster ducts.

 

[chengny]

my question now is why is it when I turn my settings to heater the air flow decreases from te dash vents and comes out the floor vents?


That is the way it is designed to work. Here is a good chart showing where the air is supposed to enter the cab for each of the selector lever positions:

You must be registered for see images attach