Blend door on A/C not working properly

Tiny
CAL CORMIER
  • MEMBER
  • 2009 NISSAN SENTRA
  • 1.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
When I first crank the car the air will blow hot or cold (what ever I have selected) through either the vents, defrost, or floor (again what ever I have selected) but once I take off and get to 60-65 MPH for a little while the door must shift because you won’t feel air coming from anyplace. You can hear the fan running at whatever speed you select but no air coming from anyplace. The first time it happened I got to the doors in the dash and found some leaves and sticks by the fan (i could hear them ticking on the fan blades). So I am pretty sure its still clean but I still have the problem. My gut tells me its a vacuum problem because like I said, if I turn off the engine, or even sometimes stop at a red light it will start working again (you can usually hear the door shift in the dash) but once I get back to cruising speed, it shuts off again.
Saturday, January 9th, 2021 AT 3:19 AM

9 Replies

Tiny
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  • MECHANIC
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More then likely this is the intake air door motor has failed. The only thing that changes with this system when you go faster is the amount of air that is going past the vehicle so I suspect this door is failing. However, I would suggest starting with removing the blower fan and make sure there is nothing still in there. It sounds like you have or had a mouse in there that built a nest. If it is cleared out then I would start with replacing this door.

Here is a guide that will help with this:

https://www.2carpros.com/articles/low-or-no-air-flow-from-vents

Let's run through this and go from there.
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Sunday, January 10th, 2021 AT 2:11 PM
Tiny
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Okay thanks, that's a start. I am pretty sure that the vent area is clean because when it works, it works great. And as I said for whatever reason if seems to work fine when idling but acts up at cruising speed, so it’s hard to mimic in the shop while working on it. Also it doesn’t matter where the selector switch is, the air isn’t coming out anywhere. So to get to the intake air motor I am guessing I have to basically take the whole dash apart?
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Monday, January 11th, 2021 AT 4:27 AM
Tiny
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Unfortunately this is the case. If this does not happen all the time then I would not just replace this door until we have more proof.

When you say you can hear the fan running, I would suggest dropping the glove box out of the way and just drive it around like this so that you can literally put your hand on the housing where the fan is and make sure it is turning. I am wondering if this is air being mistaken for the fan. If the fan is running then you should feel air somewhere.

I attached the process below on how to remove this actuator for your review.
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Tuesday, January 12th, 2021 AT 5:41 PM
Tiny
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Thanks for the response. No, the fan it running, I know it because I can hear it get louder as I increase the speed on it. You can kinda feel air coming from whatever position you have selected but it's not wide open. With the fan on high (you can hear the fan running its ass off) you barely get any air from the vents. So yesterday I drove it to work (around 7 miles). From the time I left my house until I got to work, wide open fan on defrost, you could barely feel the air coming out. After being parked all day I get in (never turned the fan off when I parked it) it worked perfectly when I cranked it back up. I went from defrost to vent and it blew my hair back all the way home. We’ll see how it wants to act when I leave today. This weekend I will take a closer look at the fan compartment and see if I left any trash in it. Again thank you.
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Friday, January 15th, 2021 AT 2:38 AM
Tiny
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Okay. That sounds good. It does sound like something is just keeping a door open that is allowing the air to escape somewhere it is not supposed to. If it is working then I think whatever it was moved and is allowing it to function. Sometimes it is good to be lucky. Maybe play the lottery today. :)
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Friday, January 15th, 2021 AT 6:13 PM
Tiny
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So if I understand, the vacuum system has nothing to do with the function of the vent doors? I was told by a friend that there is a “check” valve in the vacuum system that could be bad. Just glancing around I was unable to locate it though. Again, thank you for the help.
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Tuesday, January 19th, 2021 AT 3:50 AM
Tiny
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Your blend doors are electrically controlled. This would be possible if they were still run off vacuum but that has not been used since about the late 90's. Most all actuators started moving from vacuum to electric starting in the 80's.
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Tuesday, January 19th, 2021 AT 7:28 PM
Tiny
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Thanks for the reply. I haven't had the time to tear the dash apart to get to the blend door switch.
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Friday, January 22nd, 2021 AT 2:01 PM
Tiny
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No problem. Time is an issue for all of us it appears. Thanks for the update. Let us know how it turns out whenever you get to it. Thanks
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Friday, January 22nd, 2021 AT 7:26 PM

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