1996 Chevrolet Blazer Logo
Posted on May 25, 2008
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Vacuum leak I have a 1996 chevrolet blazer s10. When i try to change the heater control switch from floor to vent or anyother position most if not all the air comes out of the defrost vent. Some say it is a leak behind the dash the other say it is a leak up by the motor. Any help would be appreciated.

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  • Anonymous Jun 12, 2008

    VENTS TO DASH DOES NOT WORK ALL AIR COMES OUT ON FLOOR OR DEFROST.

  • bigler Nov 20, 2008

    I have a 97 Chevy blazer, 4 wheel drive with a 4.3. I was having aproblem with the vents, they would randomly select and changethemselves from what was selected. As well While driving, when theblower is on in any mode... it started clicking and clinking from timeto time like a solenoid was going out or something. Tonight I tried the heat/defrost... it blew... but no heat now.
    Themotor and everything are like new and all the ac underhood is new andgreat... this clunking is new though... from about 2 months.
    Any help on this matter or how to fix it would be appreciated, thank you in advance.
    Iknow this might be a vacuum advance or some other switching issue... soplease point me towards where to look / what to replace.
    Thanks, -Steve
    Feel free to write me directly as well:
    [email protected]

  • dusty91 Jan 05, 2009

    I am having the same problem with the AC and getting it into 4 wheel drive. Where do you think the vacuum leak is?

  • kosrae71 May 11, 2010

    i have a 96 chevy blazer. how do i take the dash off in order to put a new stereo in.

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  • Posted on Dec 14, 2009
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I have a 1992 chevy blazer s-10 type my heater blowes through the defrost and floor will not blow through vents on dash can you please help with problem thank you frank

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  • Posted on May 25, 2008
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I would say its in the dash unfortunately you will have to pull it out to inspect.

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  • Posted on Dec 27, 2008
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Hey there. I've got a 96' blazer and this happened to me as well. Turned out that I was getting the 4 wheel drive checked out because it wasn't engaging and they found that a vacuum hose was loose. The mechanic said that when it is a vacuum hose, the blower won't engage correctly to the desired setting... usually just blows out the defrost. Hope that helps.

Ben

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  • Posted on Jan 13, 2009
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Your air leak is in the heater control switch. You have to replace this unit. I have done this in both S10 Blazer and S15 GMC. Remove the front dash cover and remove the control bolts. One control is electric and the other is air controled. You can get this unit from GM or take your chance and buy it from the wrecking yard or off EBay.

Now some one also posted that there 4X4 is not working also. This uint is controled by electronic control. The transfer case has a electric motor on it and is control by the switch on the dash only. There is a canister outside under the front right (pass) side fender that controls the locking gear for the front drive axel Chech this for air leaks.

Now for the banging in the heater unit. It is the blower motor. I have the same problem right now in my S15. It needs to be changed.

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Related Questions:

0helpful
2answers

The heater core is going bad in my blazer, but it still blows hot air. When I turn the control to switch the heat from vent to defrost or floor, it still blows out of the vent. How do I fix this?
THAT HAS NOTHING TO DO WITH A HEATER CORE IF CORE IS GOING OUT IT WILL LEAK THATSOUNDS LIKE AN ACTUATOR ACTING UP OR VACCUUM LINE LEAK BEHIND DASH
Read full answer
Apr 06, 2011 • Chevrolet Blazer Cars & Trucks
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Heater will not switch to floor vent
Heater door diaphram not working, either has a vacuum leak or the main control needs to be replaced. The A/C-Heater switches work with both electricity/vacuum at the same time, the switch may be bad, replace it.
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Oct 20, 2010 • 2003 Chevrolet Blazer
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Vacuum on heater turn blower on it blowes through defrost and floor will not blow through dash vents I can't seam to be able to find vacuum l eak. Can someone please help 1992 chevy s10 blazer
your leak is probably in the control unit itself . try checking the vacum conection on the heat control
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Dec 14, 2009 • 1992 Chevrolet S-10 Blazer
1helpful
2answers

Heater will not change from defrost, and is not
The 4X4 vacuum switch has gone bad and needs to be replaced, you can pick that switch up at Auto Zone or Parts Source for around $25.00 and the dealer for $65.00. Auto Zone can give you the step by step instructions to replacing it with common tools. It's located on the top of the Transfer Case drivers side, disconnect the three vacuum line clip from it and unscrew the vacuum switch with an 1 inch open end wrench. It's going to be a tight fit to get the wrench there, but can be done. I have a spare switch in my glove box, been there done that more then once. Once new switch installed, clip the vacuum lines back in and your good as new. As for the Defroster vent, it is the switch it self on the dash which works like a vacuum line valve to the different settings like defrost, vent or floor and at worst it's going to be the actuator vent door. But most of the time it's going to the the switch it self on the dash and you can pick that up at the parts store mentioned above or the salvage yard if you would like to practice on a salvage yard car first before you take yours apart. It take about 15 min to replace the switch from the dash from start to finish which is much faster then the 4X4 vacuum switch under the truck. Good luck and be safe.
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Dec 14, 2009 • 1996 Chevrolet Blazer
2helpful
2answers

Air vents are stuck in the floor and defroster mode in my 96 Blazer. Air will blow cold and hot, just can't change where it blows. Please advise
The HVAC door actuators are powered by vacuum, and the default position is the defrost/floor. Check for a disconnected or broken vacuum line somewhere near the passenger rear of the intake manifold. You should be able to find a line coming out of the firewall in the same area and follow it to the intake. Good luck
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Nov 05, 2009 • 1996 Chevrolet Blazer
2helpful
1answer

The heater control does not change the air flow to any one position, all vents seem to be open at one time.All the fans ,air & heat work, but the air flows from all vents on this 2003 s10 pickup.
Check any vacuum hoses from engine all the way to heater/a/c housing under dash,for leaks. Then manually move or put a vacuum guage on every vac motor you can see and get to. Your working your way back to the switch. If you want to you could start at the switch but % wise and degree of difficult your better to back in. Now a schematic will make the process easier. Hard to work on a system you don't know .Electrical or Computer sometimes play into these, I have an older S10 so no computer.
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Sep 29, 2009 • 2003 Chevrolet Blazer
4helpful
2answers

1996 chevy blazer my air on heater will not blow
the idea of the switch is run on vacuum and is not making contact with the switch it self either worn contacts in the switch itself **** as an obstruction as well or the vent door is stuck in just that position either behind the glove box or the ash tray are the vacuum lines one of them may be pinched off or the door needs a bit of help until you can free it up
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Sep 08, 2009 • 1996 Chevrolet Blazer
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How can I locate the blend door for the heater/defroster
you have a bad control switch.
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Mar 04, 2009 • 2004 Chevrolet Blazer
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Heater control 98 chevy s10 blazer
These trucks have a problem where moisture builds up in the heater box then freezes. When this freezes and you change your heater settings it breaks the shaft for the blend door. If this is what happened you should be able to look under the dash above and to the right of the gas pedal and you will see two vaccuum accuators one of them you should be able to wiggle around the linkage if it is broke. To fix this you need to remove the entire dash to get the heater box out which involves discharging the AC and draining the coolant because the heater core and evaporator come out. Please rate.
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Dec 13, 2008 • 1996 Chevrolet Blazer
0helpful
1answer

Takes at least 3 tries to start
check under the hood for vacuum leaks this could cause both the heater and the running problem

your flap is controled by engine vacuum and if there is a hose off under the hood you may fix both problems
Read full answer
Sep 28, 2008 • 1996 Chevrolet S-10 Pickup
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The heater core is going bad in my blazer, but it still blows hot air. When I turn the control to switch the heat from vent to defrost or floor, it still blows out of the vent. How do I fix this?

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