Under the hood... There is a small "red" vaccuum tube from the firewall to the bottom of a canister on the passenger side and to a "t-tap" on the block. Mine got melted after a tune-up and I had to cut a small section out and replace it. A friend of mine had his disconnected after servicing at the dealer.
Answervacuum not reaching vacuum direction selector (you might think it is a switch) ( next to your ac on off control)but in actuality it changes the direction that the vacuum flows (draws) if no vacuum reachs selector, vacuum motor will stay in defrost position. I found my problem to be vacuum line disconnected under dash.
the heat blows out the defrost when it should blow out floor vents only
There may be several reasons why the air only blows out the front vents and not on the floor or the defrost on the 2003 Dodge Ram. The fuses may be blown, or the heating coil is not working correctly.
Most likely a bad or disconnected vacuum hose to the defrost/floor selector in the heater ducting.
Cold air from the defrost indicates that the air doors are in the wrong position. The doors are vacuum controlled in most vehicles. check the vacuum system for a leak.
why dont bottom vent doors not open on 2001 gmcsonoma
You lost the vacuume supply coming from the engine, defrost is the default mode if a mafunction in the vacuume supply is lost.
The first thing that you need to check will be the vacuum hoses for leaks, breaks or loose fitting ones.....
The 1984 Buick uses vacuum lines to change air flow from defroster to ac vents. Check the entire vacuum system for leaks.
ihave a 1986 chevette that when i turn defrost on it blows out heat and when i put heater on it blows out only cold air? ihave a 1986 chevette that when i turn defrost on it blows out heat and when i put heater on it blows out only cold air?
This is the same on all cars. When the air flow is OFF in a section, the it blows stronger to the other vents. In this case the ones for the windshield. This makes defrosting quicker so you can start driving safely sooner.
Loss of vacuum supply to the HVAC controller. The vacuum supply comes from the pass side of the engine and goes through the firewall next to the AC lines. It is a small black line.
Because your battery terminals are rusty. Have your dad clean them, and then check it again.