Before You Begin:
* Consult a Repair Manual: A Haynes or Chilton manual specific to your year and model Blazer is absolutely essential. It will provide detailed diagrams, torque specifications, and crucial steps you'll miss in a general description.
* Disconnect the Battery: This prevents accidental shorts and damage to electrical components.
* Gather Tools: You'll need a variety of tools, including screwdrivers (Phillips and flathead), sockets (various sizes), wrenches, pliers, and possibly a trim removal tool to avoid scratching the dashboard.
General Steps (Highly Simplified and May Vary):
1. Dashboard Removal (Partial or Full): This is the most challenging part. You'll likely need to remove the radio, various trim pieces, and possibly the instrument cluster to access the heater box. The process often involves removing screws, clips, and possibly some wiring harnesses. Your repair manual will detail the specific order and method.
2. HVAC System Disconnection: Disconnect the hoses, wires, and linkages connected to the heater core and blower motor. Carefully label everything to ensure proper reassembly. Take pictures as you go!
3. Access to the Heater Box: Once the dashboard is sufficiently disassembled, you should gain access to the heater box itself. It's usually located behind the dashboard, often near the firewall.
4. Remove the Heater Box: This usually involves removing screws and possibly bolts securing the box. Pay close attention to the placement and orientation of the box before removing it completely.
5. Remove the Heater Core (If Necessary): If you're replacing the heater core, you'll need to carefully remove it from the heater box. Be prepared for coolant spillage.
6. Reassembly: Follow the disassembly steps in reverse, ensuring all connections are secure and all components are correctly aligned. Refer to your repair manual for torque specifications.
Important Considerations:
* Coolant: Be prepared for coolant spillage. Drain the cooling system before starting.
* Wiring Harnesses: Carefully disconnect and reconnect all wiring harnesses to avoid electrical problems.
* Clips and Fasteners: Keep track of all clips, screws, and fasteners. Use plastic trim removal tools to avoid damaging parts.
* Patience: This is a time-consuming job. Don't rush the process.
Recommendation:
Unless you have significant automotive repair experience, it's strongly recommended to take your Blazer to a qualified mechanic for heater box replacement or repair. The complexity of the dashboard removal and the potential for damage makes this a job best left to professionals. The cost of professional repair may be less than the cost of replacing damaged parts due to improper removal.
