No air coming out of the vents?

Tiny
LYNN N LEIGH LILLY
  • MEMBER
  • 1999 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 20,000 MILES
There is no air coming out of the vents, fan works okay. No matter where you put the control vent, floor, or defrost no air comes out vents.
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Thursday, May 18th, 2017 AT 11:01 PM

22 Replies

Tiny
HMAC300
  • EXPERT
Try pulling heater/A/C fuse inside truck It may reset actuators. If not it may be the mode actuator that is bad. It is above gas pedal. See picture.
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Friday, May 19th, 2017 AT 6:42 AM
Tiny
DECOOP
  • MEMBER
  • 1999 CHEVROLET SILVERADO
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 378,379 MILES
Stays on defrost will not redirect to inside or floor vent
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Monday, July 27th, 2020 AT 10:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
You are dealing with a vacuum leak. Check under the dash for damaged hoses, cracked ones, dry rotted.

If you are lucky, with the engine running, you will hear a hissing sound from the leak which will help locate it.

Let me know what you find.

Joe
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Monday, July 27th, 2020 AT 10:55 AM (Merged)
Tiny
HOPEFA1TH
  • MEMBER
  • 1999 CHEVROLET SILVERADO
  • 4.3L
  • 6 CYL
  • 260,000 MILES
Will not change to floor or A/C vents.
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Monday, July 27th, 2020 AT 10:55 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi:

It sounds like the mode door actuator isn't working. That is what changes air flow direction. First, take a look through this link:

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

Here are the directions specific to your vehicle for replacing the mode door actuator. The attached pictures correlate with the directions.

_________________________________________

1999 Chevy Truck C 1500 Truck 2WD V6-4.3L VIN W
Mode Actuator Replacement
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Procedures Heating and Ventilation Mode Actuator Replacement
MODE ACTUATOR REPLACEMENT
REMOVAL PROCEDURE

pic 1

1. Remove the floor air outlet duct extension (1) from the floor duct (2).

pic 2

2. Disconnect the electrical connection at the mode actuator (10).

pic 3

3. Remove the mode actuator mounting screws from the HVAC module.
4. Remove the mode actuator as an assembly with the actuator cam.

INSTALLATION PROCEDURE

pic 4

1. Install the mode actuator as an assembly with the actuator cam.
- Line up the heater/defroster valve lever with the mode actuator cam slot.
- Line up the A/C valve lever with the mode actuator cam.

NOTE: Refer to Fastener Notice in Cautions and Notices.

2. Install the mode actuator mounting screw to the HVAC module.

Tighten
Tighten the mode actuator mounting screw to 1.6 N.m (14 lb in).

pic 5

3. Connect the electrical connection at the mode actuator (10).

pic 6

4. Install the floor air outlet duct extension (1) to the floor air duct (2).

___________________________________________

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

Take care,
Joe
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Monday, July 27th, 2020 AT 10:55 AM (Merged)
Tiny
OLERIM20
  • MEMBER
  • 1997 CHEVROLET SILVERADO
  • 165,000 MILES
1997 Chevrolet Silverado K1500 4x4, 5.7 Liter V-8

The control **** which selects if air blows out the defrost, front, foot, or etc vents operates perfectly and the blower motor does also. When moving the control **** from foot to defrost (as one example) you hear a air whistling sound and then I hear a door flap open abruptly then the air blows out the correct vent.

What is the mechanism called that controls which vent the air flows to?
Is this is likely what I need to replace?

Thanks
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Monday, July 27th, 2020 AT 10:55 AM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Vacuum master select switch
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Monday, July 27th, 2020 AT 10:55 AM (Merged)
Tiny
OLERIM20
  • MEMBER
I appreciate the help as I have always had good luck with replies on this website.

Just to be sure, since I will be buying this part and then replacing it with help of my Chilton repair book.

The "Vacuum Master Selector Switch" is what I need to buy /ask for at the parts counter, and this should allow whatever door is sticking in the vents to operate correctly and direct airflow? I wonder because my switch at the instrument control panel works perfectly (just double checking I am buying the correct part for the problem described in my previous post)

Please confirm this is the only part I need to buy and provide a beginning idea of where this part is installed in my truck.

Thank you very much !
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Monday, July 27th, 2020 AT 10:56 AM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Not seeing truck can't say if switch is fix. You asked what part was what you decribed is common to switch. Also called Mode select switch need to remove control panel
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Monday, July 27th, 2020 AT 10:56 AM (Merged)
Tiny
HROD68*
  • MEMBER
  • 1999 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
It only blows out out the vents on top of my dashboard.
Help please !
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Monday, July 27th, 2020 AT 10:56 AM (Merged)
Tiny
KASEKENNY1
  • EXPERT
This is due to the mode door motor/actuator. I attached the process on how to replace it. Let me know what questions you have. Thanks
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Monday, July 27th, 2020 AT 10:56 AM (Merged)
Tiny
HROD68*
  • MEMBER
I replaced the door motor actuator, and the air come out of the defroster area only.
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-1
Monday, July 27th, 2020 AT 10:56 AM (Merged)
Tiny
KASEKENNY1
  • EXPERT
I am sure you have electrical actuators and not cable connected so we need to remove the actuator and keep it connected to the connector and then try to change the position. We need to see if the actuator will move or not. If it moves then the door is stuck. If not, we need to start checking voltage. Let us know what you find and then we can go from there. Thanks
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Monday, July 27th, 2020 AT 10:56 AM (Merged)
Tiny
DJNOTT
  • MEMBER
  • 1996 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 207,000 MILES
When I turn the fan on you can hear it running but the air flow seams to be comming out of all the openings. You never get that blast to the windshild, dash vents, or floor. Maybe a little more comes out when you adjust to 1 of those settings. It heats or cools fine, it just takes a while. As it seems like the air comes out all the opens. Where should I start? I've always wondered if something fell down the defrost opening and is blocking something, although Ican't heat any vaccum noise when changing between the openings.
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Monday, July 27th, 2020 AT 10:57 AM (Merged)
Tiny
BLUELIGHTNIN6
  • EXPERT
Hello and thanks for donating

If the ventilation controls are not working properly then it could be bad wiring or faulty HVAC control module. Best thing to do is narrow it down, to do so just follow steps below.. let me know if you need further assistance with this issue.


https://www.2carpros.com/forum/automotive_pictures/261618_Noname_2366.jpg

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Monday, July 27th, 2020 AT 10:57 AM (Merged)
Tiny
ACE MECH
  • MEMBER
  • 1995 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
My 1995 silverado z71 has HVAC issues. Start truck, a/c selector to max, directional control to vent, blower on high, in this configuration the a/c temporarily blows cold then switches over to very HOT air. Much hotter than outside air temp. From this configuration go to blower still high, a/c still at max, directional control to defrost and tada cold air blows from the defrosting vents. Turn blower to the OFF position, directional control to vent, leave a/c selector on max (as if it would matter) and the air blow out so hot it melts my face. These results do not change with cabin recirculation button on or off. Any help is greatly appreciated as it is reaching 100 deg in Texas now. Thanks, David Elder
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Monday, July 27th, 2020 AT 10:57 AM (Merged)
Tiny
JACK42
  • EXPERT
Will it do the same thing if the blower is set to low? If not, it sounds liek the blend door actuator is weak and cant hold the door closed when theblower is on high moving alot of air.I have seen this before on an older Chevy truck. The actuator is on the bottom of the HVAC box, use a mirror to see if the shaft moves when you put the blower on high
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Monday, July 27th, 2020 AT 10:57 AM (Merged)
Tiny
KELLYANDMERLA
  • MEMBER
  • 1993 CHEVROLET SILVERADO
  • 113,000 MILES
I can see a cable connection hanging down, but I am unable to hook it back up in the space available. I would like detailed instructions to what to remove and how, so that I may get to the place to hook the cable back up. The air now blows in either defrost or on the floor only.
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Monday, July 27th, 2020 AT 10:57 AM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Which cable? What side of the dash?

Roy
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Monday, July 27th, 2020 AT 10:57 AM (Merged)
Tiny
KELLYANDMERLA
  • MEMBER
The cable controls the air flow to the vents in the dash that would blow right on you. It is on the driverside.
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Monday, July 27th, 2020 AT 10:57 AM (Merged)

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