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A/C blowing hot

Tiny
JSHEEDY1990
  • MEMBER
  • 2013 NISSAN SENTRA
  • 1.8L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
My A/C blows hot or outside temperature air, heat and defrost work fine, car idle drops slightly when A/C button is pressed. Car is full on Freon but I can hear a slight hissing noise behind dash when A/C is turned on, this has been happening for months and system hasn’t lost any pressure but still hot air.
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Sunday, June 13th, 2021 AT 11:27 AM

9 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Hi,

There is a chance the blend air door (air mix door) actuator is not working. This actuator is what determines the air temperature entering the vehicle.

What I would suggest is to remove it from the HVAC box and while it's still connected to power, see if it responds when you change from hot to cold on the controller.

This actuator is behind the glove box. If you look at pic 1 below, I highlighted the actuator. Pic 2 includes the directions for removal and replacement.

The last two pics show how the glove box is removed.

Note that I am basing this on a manual system. If this vehicle has dual climate control and automatic temp control, let me know.

Also, here is a link you may find helpful. It explains how to replace a blend air door in general. I'm adding it because the directions from my manual are somewhat vague.

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

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.
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Sunday, June 13th, 2021 AT 9:40 PM
Tiny
JSHEEDY1990
  • MEMBER
  • 6 POSTS
It’s moving under the dash but that only controls the area like head or feet, when I spin the dial to cold nothing happens.
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Monday, June 14th, 2021 AT 4:16 PM
Tiny
JSHEEDY1990
  • MEMBER
  • 6 POSTS
But there is a noticeable difference between the air when it’s on heat and cool it’s just when it’s on cool with the A/C on, it doesn’t cool the air at all. The Freon is still showing full, when you turn the A/C on the RPMs drop about 3-400 but it’s in a position I can’t see with my own eyes the clutch engaging. The actuators moved the air from head to toe to defrost smoothly but couldn’t find anything that would control the air from hot to cold under the dash.
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Monday, June 14th, 2021 AT 4:40 PM
Tiny
JSHEEDY1990
  • MEMBER
  • 6 POSTS
I found the one you referenced on the drivers side, it’s working properly.
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Monday, June 14th, 2021 AT 4:59 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Hi,

The video was the mode door actuator. That changes the airflow direction. If the compressor is working and it is fully charged, that actuator has to be causing an issue. At this point, I would recommend removing it to confirm nothing is disconnected or damaged.

If it is working properly, there is an issue with the AC system. If you turn the on, open the hood and listen. The compressor clutch will make a click sound when it engages and disengages. See if that is happening. Also, take a look through this link you may find it helpful:

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Let me know.

Joe
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Monday, June 14th, 2021 AT 8:31 PM
Tiny
JSHEEDY1990
  • MEMBER
  • 6 POSTS
Sorry for the late reply, I’ve been out of town for work so the car got set to the side for a minute.

I removed the passenger tire and inner fender and confirmed with my own eyes that the compressor is engaging and disengaging, with gauges the refrigerant reads 47 PSI “In the green”. I’ve removed the plastics on both floor compartments and confirmed all actuators are moving. I haven’t removed them to confirm they’re physically moving the doors inside.I’ve checked all fuses and relays I know to check. The things I find odd are a very slight hissing from somewhere behind the dash or the firewall, the A/C lines under the hood don’t get cool, the air seems to be slight cooler on defrost than any other mode, but I could be imagining it. Also the “evaporator” I guess it’s called lines are very hot to the touch on the drivers side, I don't know if this is weird or not, I assumed it to be what I’ve always called a “heater core” I’ve tried to look for lose vacuum lines but don’t really know where to start. I'm not at all an HVAC mechanic but it’s kind of become personal so if I can fix this myself somehow I’d love to be able to figure it out but I’m stumped.
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Monday, June 21st, 2021 AT 5:56 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
The condenser lines are normally around 100 degrees. Since the compressor is cycling, then it isn't a Freon level issue. The 47 PSI I assume is the low side pressure when checking and the ambient temperature outside was approximately 90°F. Is that correct?

If it is, then the low side pressure is good. This leads us to two things. One, we need to confirm the actuators are actually moving the blend air doors or we need an A/C manifold gauge set. You may be seeing 47 psi on the low side, but the high side may be the same or close. That would indicate a bad compressor. At 90 degrees outside, the high side pressure will be around 260 PSI.

Here is a link that explains how to evacuate and recharge the system. I'm not suggesting that, but I wanted you to see the gauges being used. Oftentimes, a parts store will lend them to you. I think the pressures need to be checked with it running so we can determine if there is a compressor issue.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Also, confirm for me the 47 PSI. Was that running, not running, and the outside temperature.

Take care,

Joe

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Monday, June 21st, 2021 AT 10:04 PM
Tiny
JSHEEDY1990
  • MEMBER
  • 6 POSTS
Yes, it was 47 PSI on the low side, car running, air on full blast and it was 92 degrees outside. I’m going to run to the parts store after work and try to loan a set of gauges. If everything checks out I’m going to dig into the actuators and see if they’re actually moving the doors or if they’ve broken off.
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Tuesday, June 22nd, 2021 AT 10:20 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Hi,

If you can, let me know what the pressures are when you get the gauges. If you find at the temp you mentioned (92 F) the low is 47 PSI, the high side should be around 260 PSI.

If it is, then the system is working. Then it will lead to the blend air door actuator. Your plans are perfect.

Let me know what you find or if there is something I Can do to help.

Take care of yourself.

Joe
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Tuesday, June 22nd, 2021 AT 7:58 PM

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