Blend Door Actuator?

1999 CHEVROLET TAHOE
129,000 MILES • 5.7L • V8 • 4WD • AUTOMATIC
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DEREKJL
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I installed a new mode door actuator (the part that controls air flow direction) the other day and had a question regarding whether or not I did it correctly. I made sure that the main dial was in the OFF position and the truck was turned off before starting. I took the old one out and put the new one in. However, I did NOT re-align the white shaft within the dash to the new actuator. Was this something I was supposed to do. I've heard of this step while replacing the temperature actuator behind the glove box but not with the mode actuator. Also, was I supposed to disconnect the negative battery cable and wait 10 minutes for the unit to "reset"? The modes work fine with the exception of a slight delay when switching from defrost to the front (face) mode. When this happens I can hear the flap inside the dash switch around. Is this normal? Thanks for any help. I appreciate your videos and have learned a great deal from them.
Apr 7, 2015 at 11:36 PM
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JACOBANDNICKOLAS
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If it is working other than a slight delay, leave it alone. You didn't do anything that will hurt it.

Here is a guide to help


https://www.2carpros.com/articles/replace-blend-door-motor


Please run down this guide and report back.
Apr 8, 2015 at 5:07 AM
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WINK1212
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I only have air/heat coming out the defrost (some slightly through the floor) and I have already replaced the blend door actuator under the floor pedals. The problems still exists, so what could still be the problem?
Jul 8, 2019 at 3:24 PM (Merged)
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HMAC300
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you need to check mode door actuator. try pulling fuse first for sixty seconds with key on it may reset and be okay otherwise see one in picture. blend door actuator is for temperature like heat to air conditioner.
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Jul 8, 2019 at 3:24 PM (Merged)
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WINK1212
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That might be what I replaced (mode door), it was under the dash above the gas pedal. I replaced it and I see if moving when I change the controls from floor to defrost, but the blower still comes mainly through the defrost. The mode door controls where the air goes right?
Jul 8, 2019 at 3:24 PM (Merged)
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STRAILER
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It sounds like the blend door itself has broken loose from inside the heater plenum. But to be sure remove the actuator and work the pivot by hand with the heater on to see if the door makes any changes.

Please let us know happens so it will help others.

Best, Ken
Jul 8, 2019 at 3:24 PM (Merged)
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WINK1212
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Ken, yeah I had did that a while back also, I pulled off the actuator and manually moved the arm up and down, but it didn't change any direction of the air/heat movement. So does that mean I need to pull the dash apart to fix?? Thanks
Jul 8, 2019 at 3:24 PM (Merged)
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HMAC300
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no you probably took the wrong one apart the pic shows correct one it may be a broken door or shaft
Jul 8, 2019 at 3:24 PM (Merged)
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GARY BURNS
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Air Conditioning problem
1999 Chevy Tahoe V8 Four Wheel Drive Automatic 150k miles

my a/c vent control does not function properly. switching from windshield to air ducts it sticks and does not complete the transition. how does this system work? how do i get at it?
Jul 8, 2019 at 3:24 PM (Merged)
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JACOBANDNICKOLAS
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Actually, in this case I believe you are looking for a vacuum leak. The vent doors are actuated by vacuum. If there isn't enough because of a leak, it will cause this. Check under the dash for damaged or disconnected hoses. Also, with the engine running, listen for a hissing sound.

AS far as access, you need to remove part of the dashboard, glovebox... to access the HVAC system and the vent doors.
Jul 8, 2019 at 3:24 PM (Merged)
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STRAILER
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If you moved the blend door pivot by hand while the unit was on and no air direction changed then yes the blend door is broken and the heater plenum needs to come out to be taken apart to see what happened.

Please let us know happens so it will help others.

Best, Ken
Jul 8, 2019 at 3:24 PM (Merged)
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KLEMM
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I have a 99 Tahoe that will not switch between defrost, vent, floor, ect... It will blow heat and A/C but will not allow me to switch between the various outputs.

Thanks for any help, it's appreciated.
Jul 8, 2019 at 3:24 PM (Merged)
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2CARPRO JACK
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Sounds like you have a broken vacuum line somewhere under the hood. Usually goes through the firwall near the a/c accumulator
Jul 8, 2019 at 3:24 PM (Merged)
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KLEMM
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Awesome, can you point me in the general direction of where the A/C accumulator would reside?
Jul 8, 2019 at 3:24 PM (Merged)
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2CARPRO JACK
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Passenger side of the firewal in engine compartment. It is a small black plastic vacuum line
Jul 8, 2019 at 3:24 PM (Merged)
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BIGGWAUKEGAN
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1st timer here so be easy on me. 97 Tahoe with new radiatior, thermostat, motor and waterpump...Heat is blowing cold but motor is not overheating. Both hoses going into firewall are warm but not hot. Could this be my heater control valve? heater door actuator? help me please its like 10 degrees here in chicago and Im cold
Sep 24, 2020 at 10:31 AM (Merged)
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RASMATAZ
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If it has a heater control valve check it-and also retest the thermostat and check the air blend door-
Sep 24, 2020 at 10:31 AM (Merged)
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BIGGWAUKEGAN
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How do i check the heater valve without replacing it? its like$11 so Ill just replace it. Gonna swap out thermostat too. would the air blend door cause cold heat?
Sep 24, 2020 at 10:31 AM (Merged)
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BIGGWAUKEGAN
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hers the ***
Sep 24, 2020 at 10:31 AM (Merged)
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RASMATAZ
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If its stuck in the cold position-check the door actuator/vacuum
Sep 24, 2020 at 10:31 AM (Merged)
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BIGGWAUKEGAN
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if the blend door is stuck in the cold position? please be more detailed with your responses. Sorry but I need details so I can get this fixed
Sep 24, 2020 at 10:31 AM (Merged)
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RACHELDART
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Replacing it under dash driver side. It’s on and wires connected but the metal arm with a gromlet won’t stay inside the circle keeps coming out. I do see the gromlet is wore out. What do I do here?
Sep 24, 2020 at 10:35 AM (Merged)
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ASEMASTER6371
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Good afternoon,

Is this the door that you have? Can you post a picture of what you see? Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

Roy
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Sep 24, 2020 at 10:35 AM (Merged)
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DAMES
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When I push the A/C button the blend door actuator rotates to open the heat door.
Sep 24, 2020 at 10:35 AM (Merged)
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STRAILER
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Hello,

What happens is the electronics inside the actuator go bad creating this issue. here is a guide to help you fix the problem:

https://www.2carpros.com/articles/replace-blend-door-motor

Please run down this guide and report back. Can you please shoot a quick video with your phone so we can see what's going on, that would be great. You can upload it here with your response.

Sep 24, 2020 at 10:35 AM (Merged)