GMT400 no defrost on drivers side

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squaredeal91

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Truck Year
1991 SB
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K30
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5.9 Cummins 12 valve
Working on a 1995 chevy 1500. Has later style dash.
No defrost on drivers side. Barely comes out pass side.
Blend door above transmission hump by column, I believe is defrost blend door and is moving fully like it should. Center one moves when I change settings. Blend door by glove box (worst one!!) Doesn't seem to be working? I also notice air coming from floor vent when defrost is on. I'm thinking I'm losing defrost air to the floor.

My question is Anyone know off hand what the blend door by glove box operates? I'm hoping it's the floor. I've replaced one before but can't remember what it did. I just remembered how hard it was lol
 

squaredeal91

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Greg bush
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1991 SB
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K30
Engine Size
5.9 Cummins 12 valve
Went and looked at a 95 without the dash and got some answers. The far right blend door motor controls bottom flapper by blower motor. The one in the truck is stuck open. Removed motor and door closed. I'm noticing more air coming from the center vents than the defrost? That's interesting.
 

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squaredeal91

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Cave junction Oregon
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Greg bush
Truck Year
1991 SB
Truck Model
K30
Engine Size
5.9 Cummins 12 valve
Looking at the 95 without a dash I noticed this broken flapper. Wondering maybe this is the issue. Also the a/c hardly blows too. Also affected by this issue I believe. I'm thinking the same thing happened to the 95 I'm trying to fix. Looks like they need an air box or an air box rehab.
 

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HotWheelsBurban

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Looking at the 95 without a dash I noticed this broken flapper. Wondering maybe this is the issue. Also the a/c hardly blows too. Also affected by this issue I believe. I'm thinking the same thing happened to the 95 I'm trying to fix. Looks like they need an air box or an air box rehab.
The doors and motors for them are prone to wearing out. Also the gaskets/seals shrink and then you get air coming out different places than it's supposed to. Blower motor also could be weak; I replaced the one on my crew cab a couple years ago and it really made me realize how worn out the original 26 year old unit was! It was getting to the point where you had to kick it or slam the door, to make it come on.... They're not as easy to change as on the squares, but if you can get the vinyl sound deadening cover off, it's easily accessible from the passenger side door. It's easier access to the bolts if you pull the glovebox assembly out, but it can be done without doing that, if you have 1/4 drive ratchet and sockets. Some are 6mm and some are 5.5mm hex head. There is probably a ground wire terminal tab , bolted to the motor bracket, and if it's the original motor, there will probably be 5 special tubular washers under the bolts. Those washers and the ground wire terminal tab will need to be moved over from the original motor; new ones don't come with them.
On my truck, I'd taken the vinyl cover off at home, so I could test the motor. I swapped them out in the parts store parking lot.
 

squaredeal91

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Cave junction Oregon
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Greg bush
Truck Year
1991 SB
Truck Model
K30
Engine Size
5.9 Cummins 12 valve
The cover is gone but blower motor is dated some day of some month in 1995 Rochester USA lol. Maybe the motor has some play in this too
 

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