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Bob, Auto Tech
Category: Chevy
Satisfied Customers: 4087
Experience:  Plus 40 years GM, over 30 certified with Chevrolet, ASE certified Master Tech. (Expired, Retired)
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1992 Chevy S10 Blazer: I replace the heater core

Resolved Question:

How do I replace the heater core in my 1992 Chevy S10 Blazer? I hear the whole dash has to come off. Help!
Submitted: 9 years ago.
Category: Chevy
Expert:  Bob replied 9 years ago.

Nope, not on a 92. You will find that if you take the 10mm bolts out of the very bottom edge of the dash pad from the brace under the radio all the way to the end on the right side that the dash will pull back far enough for the core to clear coming out. I have also found that if you remove the ash tray, bezel and cigar lighter and radio and such that you can use a real long 1/4 inch drive extension and a wobble socket to remove the little screws that hold the case together I think they are 7 mm. Also on the right side be careful not to break the antenna lead in coax where it is secured to the right side heater case plastic. Here you will need a short extension and look at the very back of the glove box to see if there is a trap door in it to access some of the case half screws. It will have 2 screws in the small door if it has one. The other thing to know is that the left side of the case may be sticky and stubborn even with all the screws out, because they use a real good grade of double sided sticky plastic tape to seal that joint with. Regular instructions below. Let me know if you get in trouble or have other questions. A small piece of masking tape stuck on the case is a good way to write down the colors of wires and vacuum hoses when you want to identify where they go when going back together with it. Good luck, take your time and you will be fine. Thanks

See Figures 1, 2, 3, 4, 5, 6, 7, 8 and 9

  1. Disconnect the negative battery cable.

  2. Position a drain pan under the radiator, open the drain cock and drain the cooling system to a level below the heater core.

Plug the heater core tubes to avoid spilling coolant in the passenger compartment during removal.

  1. Disconnect the heater-to-engine coolant hoses from the core tubes on the firewall, in the engine compartment.

Click image to see an enlarged view
Fig. 1: Exploded view of a common heater core and case assembly


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Fig. 2: If necessary, loosen and remove the under dash cabin light retaining bolt


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Fig. 3: With the bolt removed, the light and housing may be repositioned out of the way


On some early model vehicles, the cabin light mounted under the dash may interfere with cover removal. If necessary, loosen the retaining bolt and reposition the light housing with the wiring attached.

  1. From the passenger compartment (under the dash) remove the heater core rear case cover-to-cowl screws, then remove the cover from the vehicle.

On a few of the early model vehicles covered by this guide, some of the heater core cover screws may be partially/fully covered by the dashboard. Be sure that all are removed before attempting to remove the cover. If necessary, unbolt and reposition all/part of the dashboard for better access.

  1. Remove the straps or brackets from each end of the heater core.

  2. Carefully remove the heater core from the cowl and case.

To install:

  1. Insert the heater core into the case, taking care not to damage the tubes as they are inserted through the cowl.

  2. Install the straps or brackets to the ends of the heater core and secure using the retaining screws.

  3. Install the heater core rear case cover and secure using the retaining screws.

  4. If moved for access, reposition and secure the dash mounted cabin light and housing.

  5. Connect the heater-to-engine coolant hoses to the core tubes.

  6. Connect the negative battery cable, then properly refill the engine cooling system.

  7. Run the engine at normal operating temperatures and check for leaks.

Click image to see an enlarged view
Fig. 4: Loosen and remove the rear case cover screws


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Fig. 5: Remove the rear case cover for access to the heater core


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Fig. 6: Loosen and remove the core strap/bracket retainers


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Fig. 7: Remove or reposition the straps/brackets so the core can be removed


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Fig. 8: Most cores are retained by straps/brackets on both ends; don't forget to loosen all retainers


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Fig. 9: Carefully withdraw the heater core from the case


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