Can't get defrost to work.
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Posting Guru
Joined: Oct 2010
Posts: 1,199
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From: Missouri
Can't get defrost to work.
Hello,
I can't seem to get the defrost to work on my (factory A/C equipped)truck. Off turns everything off, Mix makes heat come out at the floor and vents. When put to "Floor" the thing under the dash opens farther allowing more air to come out at the floor, but it still blows out the vents. Defrost still blows out the vents. A/C seems to work, I hear something and the fan changes tone. (I don't have a compressor or anything)
No matter where I put it I can't feel any air blowing out the dash, I even unhooked the vacuum line that runs into the cab and it still blows from the vents. Manually, what does it take to make the defrost work, like can I put my hand under the dash and do something just so I can actually feel the air? Would it be useful to remove the dash pad or does that not provide any more visibility..?
I can't seem to get the defrost to work on my (factory A/C equipped)truck. Off turns everything off, Mix makes heat come out at the floor and vents. When put to "Floor" the thing under the dash opens farther allowing more air to come out at the floor, but it still blows out the vents. Defrost still blows out the vents. A/C seems to work, I hear something and the fan changes tone. (I don't have a compressor or anything)
No matter where I put it I can't feel any air blowing out the dash, I even unhooked the vacuum line that runs into the cab and it still blows from the vents. Manually, what does it take to make the defrost work, like can I put my hand under the dash and do something just so I can actually feel the air? Would it be useful to remove the dash pad or does that not provide any more visibility..?
Moderator
Joined: Nov 2007
Posts: 22,415
Likes: 92
From: Denver Metro Area, CO
Removing the dash pad offers GREAT visibility & access, I haven't had mine installed for years for that very reason.
Removing the glove compartment and radio also sometimes helps, too.
Removing the glove compartment and radio also sometimes helps, too.
Posting Guru
Joined: Feb 2011
Posts: 2,216
Likes: 0
From: Princeton MN
Mine has been doing the same, the way it seems to me is the VENT door is hanging up, on mine if I don't use the vents for a few days and go bouncing down the road the door will close, once closed if you slide your selector very quickly to defrost so the vent door don't accuate you will have defogs. I haven't gotten around to taking the dash apart yet. Could be one of 2 things, there is foam from the door seals stuck in there, or the hinge my have broken or come loose from what I have been told.
Lead Driver
Joined: Jul 2009
Posts: 6,477
Likes: 19
From: Sheffield, AL
Sw1tchfoot,
I just did a quick search and found three threads which will be of assistance.
Heater Blend Door Gone Bad - Calling NumberDummy [11/21/2011]
HVAC problem [7/30/2011]
HVAC vent / door problems (WAS: my 86 F250 haunted) [11/12/2010]
I just did a quick search and found three threads which will be of assistance.
Heater Blend Door Gone Bad - Calling NumberDummy [11/21/2011]
HVAC problem [7/30/2011]
HVAC vent / door problems (WAS: my 86 F250 haunted) [11/12/2010]
Fleet Mechanic
Joined: May 2005
Posts: 1,575
Likes: 11
From: Puyallup, WA
Very common problem. Assuming you have verifed that the vacuum motor is moving the link rod (and I have never seen one of these fail) The vent door hinges have failed, they are just a plastic material. Pull the glove box, pull the cover off of the heater box and you will have enough room to access the door area and replace it. You have to spread the heater housing a little bit as well. All in all not a hard or bad job at all.
I beleive at this late date these are obsolete, but I bet Number Dummy can find one for you.
David
I beleive at this late date these are obsolete, but I bet Number Dummy can find one for you.
David
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