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

15 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)

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