I notice when I’m driving the heat is blowing through the vents but it’s off?

Hi,

If the car fogs up quickly, often times that indicates that fresh air isn't entering the vehicle. Instead, recirculated air is being used.

You mentioned a knocking sound. Is it coming from under the dash?

I attached two pics below. The first is the mode door actuator. That determines where air exits the HVAC from, the floor, defroster and so on. The second is the air intake door motor. That is what allows fresh air to make it into the vehicle or recirculate inside air.

Here is what happens. Often times the small plastic gears in the actuators will break. As a result, you will hear a clicking sound. That is what I think you are hearing.

The best thing I can tell you is to either locate the parts I mentioned and see if one of them is making the noise, or remove them one at a time for inspection.

Note, you should be able to access them by removing the glove box.

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Let me know if this helps or if you have other questions.

Take care,
Joe

Hi,

It shouldn't do that and you should have control of the temp. The temperature is controlled by a blend air door (AKA Air mix Door) and there is an actuator for that as well.

Since you hear the noise behind the left side of the dash, it's one of them that is causing the problem. I need to know if the system is automatic climate control or manual. Also, I need to know if you have dual climate control.

Take a look at the pic attached. It shows the blend door (air mix door) for a manual system. This makes more sense to me simply because there is only one that controls both sides.

What I suggest is to either remove it and inspect the gears and see if it operates when you change temperature request. Or, simply replace it. It's on the right side of the HVAC box under the dash and behind the glove box.

If you want, here are the directions for replacement:

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2013 Nissan-Datsun Altima Sedan L4-2.5L (QR25DE)
Removal And Installation
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Removal and Replacement Manual Air Conditioning Air Mix Door Motor Removal And Installation
REMOVAL AND INSTALLATION
DOOR MOTOR

AIR MIX DOOR MOTOR : Removal and Installation

REMOVAL

1. Remove the glove box assembly. Refer to "Removal and Installation" See: Glove Compartment > Removal and Replacement > Removal And Installation.
2. Remove the upper floor connecting duct RH. Refer to "Exploded View" See: Housing Assembly HVAC > Removal and Replacement > Exploded View.
3. Disconnect the harness connector from the air mix door motor.
4. Remove the air mix door motor screws and the air mix door motor.

INSTALLATION

Installation is in the reverse order of removal.

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Here are additional directions to help.

2013 Nissan-Datsun Altima Sedan L4-2.5L (QR25DE)
Removal And Installation
Vehicle Body and Frame Interior Moulding / Trim Glove Compartment Service and Repair Removal and Replacement Removal And Installation
REMOVAL AND INSTALLATION
GLOVE BOX ASSEMBLY

Removal and Installation

REMOVAL

1. Remove the instrument side finisher RH using a suitable tool.

Pic 2

2. Remove the glove box assembly (1) upper screws (A).

Pic 3

3. Remove the glove box assembly lower screws (A).
4. Disconnect the harness connectors from the trunk switch and glove box lamp, then remove the glove box assembly.

INSTALLATION

Installation is in the reverse order of removal.

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2013 Nissan-Datsun Altima Sedan L4-2.5L (QR25DE)
Exploded View
Vehicle Heating and Air Conditioning Housing Assembly HVAC Service and Repair Removal and Replacement Exploded View
EXPLODED VIEW
HEATING AND COOLING UNIT ASSEMBLY

Exploded View

pic 4

pic 5

_________________________

Let me know if this helps or if you have other questions.

Take care,
Joe

Hi,

I'm not sure how the radio would be related. However, I feel somewhat confident it is one of the actuators I mentioned. Do me a favor. Read through the first few paragraphs of this link and let me know if it seems to make sense as far as what I'm suggesting.

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

Let me know.
Joe