How to change heater core

Tiny
TJ DOPORTO
  • MEMBER
  • 1999 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 173,069 MILES
I would like to know how to open the evaporator box on a the vehicle listed above (s10) in order to change the heater core?
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Sunday, January 31st, 2010 AT 5:55 PM

111 Replies

Tiny
RASMATAZ
  • MEMBER
Hello,

You will need to start by disconnecting the battery and discharging your AC system.

Here are two guides and diagrams with the instructions below.

This will give you an idea.

https://www.2carpros.com/articles/replace-heater-core

Here are the AC instructions:

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

Check out the diagrams (below). Please let us know if you need anything else to get the problem fixed.

Cheers
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Sunday, January 31st, 2010 AT 6:09 PM
Tiny
BAMAGEOFF
  • MEMBER
  • 1999 CHEVROLET BLAZER
Hello, I have a 1999 S10 Blazer with 67,000 miles. My heater core began to leak Dexcool into the evaporator box. I flushed it out and by-passed it with a union (heater core is now unattached from the coolant loop). I took the dash all of the way out of the vehicle to replace the heater core and noticed I needed to remove the heater/evaporator box in order to gain access to the heater core. My question is, instead of taking the evaporator box all of the way out, can I get to the core by cutting the plastic evaporator box, change the core, and plastic weld the evaporator box back together? This would be a major time saver for me if possible.

I appreciate any help you can provide.
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
If it is going to work for you playing shortcut do it, but remember if it is not done right, you will be going back in.
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
GUESSING
  • MEMBER
  • 1999 CHEVROLET BLAZER
I have removed the dash. I am stuck on removing the HVAC unit. I have removed the bolt inside the resistor compartment, nut on stud next to inlet in engine compartment and lower right bolt inside car. Cannot find any other bolts but it is still in solid. What am I missing? Thanks for any help.(4.3L, 4WD, A/C)
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
SUNNY12888
  • MEMBER
  • 1999 CHEVROLET BLAZER
Six cylinder two wheel drive automatic

I am having trouble figuring the easiest way to go about removal of the heater core. Any tips? Cannot get a Chilton's right now.
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
BMRFIXIT
  • EXPERT
Removal & Installation ("C" & "K" Series)
Disable air bag system.
Disconnect negative battery cable.
Remove glove box by squeezing sides together. Remove 2 instrument panel retaining bolts from glove box opening.
Remove center floor duct.
Remove center support bolt.
Remove Electronic Control Module (ECM) and tray. Remove both kick panels.
Remove blower motor cover and blower motor.
Remove driver's lower instrument panel cover and knee bolster.
Lower steering column.
Remove instrument panel left and right pivot bolts located at lower corners of instrument panel. Remove 3 screws from defrost vent, near windshield. Disconnect any connectors and tilt instrument panel back far enough to access heater case.
Remove coolant recovery reservoir from engine compartment.
Drain engine coolant. Disconnect heater hoses at core.
Remove bolts and nuts from engine compartment attaching heater case to vehicle.
Remove heater case.
Remove 7 screws attaching heater case cover plate. Remove screws and bracket attaching core to case. Remove heater core.
To install, reverse removal procedure.
Replace any seals.
Fill cooling system. Start engine and check for leaks.

Removal & Installation ("S" & "T" Series)
Disconnect negative battery cable.
Drain engine coolant.
Disconnect heater hoses at core.
Remove instrument panel. .
Remove air inlet assembly.
Disconnect vacuum lines to heater case components. Remove heater case retaining studs from engine compartment. Disconnect blower motor resistor. Remove heater case. Remove heater core access cover from top of heater case. Remove heater core. Remove seals. To install, reverse removal procedure. Fill cooling system. Replace old seals with new seals. Start engine and check for leaks.


http://www.2carpros.com/forum/automotive_pictures/99387_Graphic1_484.jpg



http://www.2carpros.com/forum/automotive_pictures/99387_Graphic2_239.jpg

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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
SORICH1
  • MEMBER
  • 1999 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • MANUAL
  • 90,000 MILES
Could you please show me a diagram or explanation of the removal of the heating ventilation module?

Thank you
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
WRENCHTECH
  • EXPERT
Believe me, this is not something that you even want to attempt. This is a major undertaking. Even for an experienced tech, this is about a ten hour job.

This involves removing the entire dash and part of the fender to get this apart. There are many experienced techs that will not attempt this.
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
MADMIKE1735
  • EXPERT
I could not have said it better myself. Wrenchtech is 150% correct with this one. The book time give 8.9 hours. That is giving a professional tech is doing the job. I have done a few, and hated each one, haha. Keep in mind, before the dash comes out, you need to disable, and remove the air bags, one wrong move, and they may deploy causing serious injuring. Leave this job to the professionals.
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
MANCHIS
  • MEMBER
  • 1999 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 124,000 MILES
How to remove a heater core?
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi, replacing the heater core is an involved process. You need to remove part of the dashboard. I recommend purchasing a manual for your car. It provides step by step instructions and pictures to help identify parts. I am unable to copy and paste from the online manual we use, and there is too much room for error if I try to explain it via the Internet.
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
ZEBSHA
  • MEMBER
  • 1999 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 57,000 MILES
Dear sirs, could you please help me by telling me how to change the heater core?
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi.
Changing the heater core on your vehicle is an involved procedure. It is located under the dashboard on the passenger side and requires much of the dash to be removed. What I would recommend is that you get a manual for the vehicle. It will provide step by step instructions with pictures to help identify parts.

I would send you the directions, but I am unable to cut and paste from the service manual we use.

If you get a manual and still need some help, let me know. I will be happy to help.

Joe
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Monday, June 4th, 2018 AT 1:07 PM (Merged)
Tiny
SHUGMISSEY
  • MEMBER
  • 1999 CHEVROLET BLAZER
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 125,000 MILES
Had my heater core replaced and now have no heat. What could be the problem?
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Monday, June 4th, 2018 AT 1:08 PM (Merged)
Tiny
MADMIKE1735
  • EXPERT
Most likely an air pocket not allowing coolant to reach the heater core lines. Run the vehicle until it reaches around 200 degrees, that will allow the thermostat to open. Then let it cool off for a while before checking the coolant level. Add as necessary.
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Monday, June 4th, 2018 AT 1:08 PM (Merged)
Tiny
FREEK_KC
  • MEMBER
  • 1997 CHEVROLET BLAZER
Six cylinder four wheel drive automatic.

I need to remove my dash so I can replace my heater core. How do I remove the dash? I know where the heater core is located, do I need to remove the entire dash, or just the dash panels where the heater core is?
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Thursday, December 27th, 2018 AT 8:13 PM (Merged)
Tiny
SWILLIAMS
  • MEMBER
The entire dash needs to come out. It is not a fun thing to do. You should have a copy of the manual to do it easily. In short you need to disconnect the battery, unbolt the steering column from the dash. There are a bunch of bolts that hold the dash in. One on each end under the dash, two or so in the middle under the dash, then there are bolts hidden behind the A/C vents behind the speaker grills and behind the defrost vent. Once they are all out the dash can be moved out of the way enough to get to the heater case. Figure about six hours if you have done it once longer if you need to learn as you go.
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Thursday, December 27th, 2018 AT 8:13 PM (Merged)
Tiny
RANDY AIKMAN
  • MEMBER
  • 1997 CHEVROLET BLAZERCHEVROLET BLAZER
1999 Chevrolet Blazer 4X4, 4.3 V6, 150k miles that has a bad heater core. The Haynes Manual that I have is incorrect. Please provide me with the correct method of removal
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Thursday, December 27th, 2018 AT 8:13 PM (Merged)
Tiny
DENNYP
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/102900_heater_1.jpg



http://www.2carpros.com/forum/automotive_pictures/102900_123_1.jpg



http://www.2carpros.com/forum/automotive_pictures/102900_22222_1.jpg



http://www.2carpros.com/forum/automotive_pictures/102900_33333_1.jpg



http://www.2carpros.com/forum/automotive_pictures/102900_44444_1.jpg

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Thursday, December 27th, 2018 AT 8:13 PM (Merged)
Tiny
DENNYP
  • EXPERT
Heater/Vent Module Replacement
Removal Procedure

Remove the instrument panel. Refer to Instrument Panel (I/P) Carrier Replacement in Instrument Panel, Gauges and Console.
Drain the engine coolant. Refer to Draining and Filling Cooling System in Engine Cooling.
On vehicles with automatic climate control only, cut (1) the outer layer of the A/C evaporator and blower module in order to access the service access cover. Refer to Blower Motor and Fan Replacement.
On vehicles with automatic climate control only, remove the service access cover mounting screws.
On vehicles with automatic climate control only, remove the service access cover.
On vehicles without automatic climate control, remove the blower motor resistor. Refer to Blower Motor Resistor Replacement.
Important: Mark and use the same mounting bolt (located behind the A/C evaporator and blower module) for the heater assembly during the installation process. Other mounting bolts are longer and will obstruct the operation of the temperature door.

Remove the heat/vent module mounting bolt through the blower motor resistor or service access cover opening.

On vehicles with A/C only, remove the right wheel house panel. Refer to Wheelhouse Panel Replacement in Body Front End.
On vehicles with A/C only, raise and support vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
On vehicles with A/C only, remove the front right tire. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
On the Utility only, remove the A/C evaporator and blower module heat shield screws.
On the Utility only, slide the A/C evaporator and blower module heat shield toward the front of the vehicle.
Remove the 2 lower heat/vent module mounting nuts.
On the Utility only, remove the A/C evaporator and blower module heat shield bracket.
Remove the bottom right heat/vent module mounting bolt from inside the vehicle.
Important: The heat/vent mounting stud has a flange on the inside and cannot be removed from under the hood. Stop turning the stud after the threads are off the heat/vent module.

On the Utility only, while an assistant inside the vehicle pulls the bottom right corner of the heat/vent module approximately 1 inch back, remove the 2 heat/vent module mounting studs.
On vehicles with A/C only, lower the vehicle.

On vehicles with a 2.2L engine only, remove the engine wiring harness bracket located at the rear of the intake manifold. Refer to Valve Rocker Arm Cover Replacement in Engine Mechanical - 2.2L.
Remove the heat/vent module mounting bolt located at the lower left side of the heater core to heater hose connection.
Remove the heat/vent module mounting nut located at the lower right side of the heater core to heater connection.
Important: The heat/vent mounting stud has a flange on the inside and cannot be removed from under the hood. Stop turning the stud after the threads are off the heat/vent module.

On the Utility only, loosen the heat/vent module mounting studs until the threads are free from the heat/vent module.
Disconnect all of the electrical connectors from the heat/vent module.
Disconnect all of the vacuum lines from the heater assembly.
Disconnect the heater hoses from the heater core.
Remove the heat/vent module from the vehicle.
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Thursday, December 27th, 2018 AT 8:13 PM (Merged)

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