I would think that is a vacuum or a linkage problem with the heater control assembly (where all the buttons/slides are for changing between floor/defrost/vent) Had a diaphragm go bad on one once, and in a jeep cherokee, a slight collision with a guard rail knocked a vac line off for the vent controls, and ac only worked from defroster.
This is a very common problem and you need to check for a vacuum leak, broken vacuum line or a loose vacuum line......
The year, make and model info would help. Also need to know if the blower motor is working, just not getting any heat, or not changing function between defrost, dash or floor vents.
Because you have a vacuum leak in the system or your vacuum canister is leaking. When you accelerate the vacuum from the engine will drop. That will cause your system to loose vacuum and the floor/defrost door will go to its neutral position. To keep the vacuum up you have a canister that will hold vacuum. It must be air tight.
on my 1992 road touring itdid the same thing and it was the computer but it only cost 102.00 from gm
Your blend door is giving you trouble, it is not switching from defrost to heat or vent
depending on what year and make it is, the most likely issue is that you have a valve that moves to divert air to the upper vents, floor vents, and defrost vents and it is either stuck in the defrost position, is broken, or a cable/connector has come loose. The valve is usually in the center of your dashboard up against the firewall. The air flow direction in many vehicles is operated by vacuum controlled servos. If the vacuum supply is cut off, the system reverts to it's default position which is the defrost mode. My guess would be that the HVAC vacuum supply line under the hood is disconnected, pinched or collapsed.
The year, make and model would help but many vehicles use vacuum to operate the direction of air flow through the floor vents, dash vents and defrost vents. If the vacuum supply is cut off for whatever reason the system defaults to defrost only. So if you only have the defrost mode working chances are the vacuum supply is cut off. Check the HVAC vacuum supply line under the hood for damage. If that system seems to be working but you have insufficient air flow through all of the vents, check/replace the cabin filter if applicable.
There are heater doors on the heat blower box that direct the path of the heat. Apparently the heater door to the floor vents is stuck closed.
Check the following.......... 1. Vacuum leak, broken vacuum line or disconnected vacuum line. 2. A/C - heater inside car door operation.. 3. A/C - heater controller..
vacuum leak the vacuum reservoir is below the left head light, check the hoses
Any of the following can cause this......... 1. Bad a/c - heater controller.. 2. Bad a/c - heater controller inside door operation.. 3. Bad, broken or cracked vacuum line/lines..
The flap that directs sir to the selected vents is jammed or broken...or the switch that controls it is.
yes it would save money :)
check your vacum line to door by the gas pedal for vacum
You probably have a jammed or otherwise defective vent door.
I had a Chevy van of this vintage and I found a vacum hose leak in the controls that would make the heater/defrost door default too defrost open. lisining carefully under dash or under hood may pinpoint leak. I had a Chevy van of this vintage and I found a vacum hose leak in the controls that would make the heater/defrost door default too defrost open. lisining carefully under dash or under hood may pinpoint leak.
I don't know why the vent would not open for the defrost, but it may be related to the fact that your heater core is blown. If your getting nothing but cold air out of the vents when the heat is on, your core is finished and if the core is finished then it is likely related to your vent not opening/switching. Something''s wrong with your heating either way.
Some ford truck hvac systems will default to the defrost setting if the is a problem with the electrical or vaccum parts of the system. I encountered a ford truck that had a mouse living under the hood and chewed through the vacuum hoses and would only blow on defrost.Do a good visual check including electrical,such as fuses etc...
Warm(er) air rises - if vents were high up there would be little circulation without fans.
Heating vents should be located near the floor since hot air rises. If the heating vents are located near the ceiling the heat would stay there and not warm the room.
The most likely cause would be a vacuum leak at the rear of the engine or a defective selector switch.
Underneath the driver side dashboard, near the center console, is a plastic control knob with a metal wire/bar connector that is attached to the main directional control knob (defrost, vent, floor vent select knob) on the center console. The metal wire/bar will sometimes pop off the plastic control knob, so when you turn the main control you're not actually re-directing the forced air to the selected vents. Re-attached the metal wire/bar to the plastic control knob and should fix the problem.
it would depend on the year of the accord. Does the defrost work or the heat in the floor work if so the line for swapping control is either broke or has come off. you can check the lower side by looking in the drivers side under the dash.
some thing is probley cloging the vents take it appart and ckeck.