Hvac blend door question...

[jayzon]

Forgive me if this is posted elsewhere, if so I was unable to find it. Through countless YouTube videos and forums I still can’t find an answer. Is the hvac blend door supposed to close completely (flush) with the case when switching to defrost? And/or open fully when on max? It operates normal yet lacks about 1/2” from closing completely, letting air through different vents. This may be normal, I have no idea. If not I’m at a loss as to what to check next. Oh, it’s an 84 GMC Jimmy Thanks!!! Edit...I didn’t see the HVAC category at first, so I posted here. New guy lol

 

[gmbellew]

when it is in defrost, minimal air comes out the heat vents. when it is heat mode. minimal air comes out the defrost vents. that is normal operation

 

[jayzon]

Thanks, had everything apart replacing the heater core and was testing the operations of all the doors before finishing up, that’s when I noticed it. Checked everything I knew to check, just odd it would be such a gap like that. I understand minimal air coming through, but would a 1/2” gap from closing completely be considered minimal? No broken clips, no obstructions etc.

 

[Ken B]

tagging on this thread.
so as I am reassembling the heater box and controls, the controls wont go all the way to the off position. which cable is out of adjustment? it is conected to 2 cables....

 

[Craig 85]

Hopefully you got this fixed. When I had my box out I repaired the factory floor/Defrost flapper. Photo #1 From the factory there is a foam seal that deteriorates over time. I bought some Scotch felt furniture pads and cut them to fit. I reused the staples the arrow points to. It created a perfect seal. Overall length was about 2".

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[Ken B]

thanks awesome idea

 

[Ken B]

Peel and stick Felt worked great

 

[neiltee]

Hopefully you got this fixed. When I had my box out I repaired the factory floor/Defrost flapper. Photo #1 From the factory there is a foam seal that deteriorates over time. I bought some Scotch felt furniture pads and cut them to fit. I reused the staples the arrow points to. It created a perfect seal. Overall length was about 2".

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I too am repairing the HVAC air diverting 'stuff' but the heater/defroster flap in my system does not return to the fully up position. Is there supposed to be a return spring? I did just replace the actuator with a new one from OLD AIR PRODUCTS.

 

[Craig 85]

I too am repairing the HVAC air diverting 'stuff' but the heater/defroster flap in my system does not return to the fully up position. Is there supposed to be a return spring? I did just replace the actuator with a new one from OLD AIR PRODUCTS.

It's been a few years since I had all that stuff disassembled. The pod that points toward the gas pedal should be the one that controls the floor/defrost flap. It's the one at the bottom of the yellow box.

The pod in the red box pushes and pulls on the blend door (second red box). That plastic piece on the door tends to break. A lot of people replace it with a billet one.

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[AaronW]

I was just trying to buy a billet aluminum one from an onine outfit called thepartsguy. Couldn't not figure out how to actually order from them. Anyone else have this problem?

Aaron

 

[75gmck25]

Unless you are stuck on that vendor, they are sold by multiple vendors, including LMC. I think you can even get them from RockAuto.

 

[84GMCSierra]

My defrost quit working a couple years ago, and I think it's the round thing that looks like a vacuum advance above the right kickpanel. I had to splice the vacuum line but can't get it to work.

 

[Craig 85]

My defrost quit working a couple years ago, and I think it's the round thing that looks like a vacuum advance above the right kickpanel. I had to splice the vacuum line but can't get it to work.

The vacuum pod on the kick panel is for Max A/C. It ties to the pod on the cowl area behind the hood(exterior of truck). There is another pod near the transmission hump that controls defrost and heat to the floor.