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What would make your ac blow out of the defrost vents if you have it on max ac or vent when you accelerate in a 1997 ford thunder bird?
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Why would the ac change from dash vents to the defrost vents when accelerating?
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.
When you accelerate in your1999 mercury mountaineer the vents close what would cause this?
Pin cone
Why would your air conditioner blow out of the defrost vents ON 2000 F-350?
You probably have a jammed or otherwise defective vent door.
Why is there no air coming out of vents can hear air blowing under dash board?
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.
Why does heater defrost vent not open on a 1989 Sunbird and cold air blow from dash vents but no air blows from heater defrost vents and where are the enter and exit hoses for the heater coil?
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.
1991 Chevy G20 van- Why won't airconditioning blow out of dash vents instead of defrost and heat vents?
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.
Why does AC and heater blow air through defrost vents and will not blow air?
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.
Why would the air conditioning only blow air from the defrost and floor vents and not the dash vents on a 1996 jimmy?
This is a very common problem and you need to check for a vacuum leak, broken vacuum line or a loose vacuum line......
The heat air and defrost do not work What is wrong?
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.
Why would the ac change from dash vents to the defrost vents when accelerating in a Ford F150?
You are having a vacuum loss. Check the hard plastic line that is on the right side under the hood for holes. I replaced mine and it fixed the problem. 1992 F150
Why would the air conditioning only blow air from the defrost and floor vents and not the dash vents?
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.
Why would you get heat out of your defrosters but not your front vents or the floor on a 98 wrangler. fuses are good and I replaced the control pannel?
Your blend door is giving you trouble, it is not switching from defrost to heat or vent
