1. Preparation:
* Disconnect the Battery: This is crucial for safety to prevent accidental shorts and electrical shocks.
* Gather Supplies: You'll need the new heater cables (ensure you have the correct gauge and length), zip ties, wire loom (optional but recommended for protection), possibly new cable clamps, and appropriate tools (screwdrivers, pliers, possibly a wire stripper/crimper).
* Consult a Wiring Diagram: A 1970 C10 wiring diagram is invaluable. You can find these online (eBay, forums dedicated to classic Chevy trucks) or in a repair manual specific to your year and model. This will show you the correct cable routing and connection points.
* Inspect the Existing System: Carefully examine the old cables (if present) to understand their routing. Take pictures before disconnecting anything. Note the condition of the existing heater core and hoses.
2. Cable Routing:
* Heater Core Connections: The heater cables connect to the heater core inside the cab. Access this by removing the dash panel (a significant undertaking, requiring patience and possibly special tools). Be gentle to avoid breaking plastic tabs.
* Firewall Penetration: The cables must pass through the firewall. There are usually existing grommets or holes. If not, you'll need to carefully create new ones, ensuring a tight seal to prevent leaks.
* Under the Hood: From the firewall, route the cables to the heater control valve (if equipped) and the heater blower motor. Try to follow the path of the old cables (if replacing) or choose a route that's secure and protected from moving parts or hot components. Avoid sharp bends.
* Securing the Cables: Use zip ties to secure the cables to existing brackets or frame members, keeping them organized and preventing chafing. Wire loom provides additional protection.
3. Connections:
* Accurate Connections: This is CRITICAL. Incorrect connections can lead to malfunctions, overheating, and even fires. Use your wiring diagram to ensure you connect the correct cables to the heater core, blower motor, and control valve (if applicable).
* Proper Terminals & Connections: Use the correct terminals and connectors. Poor connections can lead to resistance and overheating. Crimp connectors securely and solder them for added reliability (though soldering might be difficult in tight spaces).
* Insulation: Ensure all connections are properly insulated to prevent shorts.
4. Testing and Reassembly:
* Test the System: Reconnect the battery and test the heater. Check for proper operation and ensure there are no shorts or overheating.
* Reassemble the Dash: Carefully put the dash back together.
Important Considerations:
* Safety First: Working with electricity and under the dash can be dangerous. Take your time, be cautious, and if you're not comfortable with the task, seek professional help from a qualified mechanic.
* Proper Gauge Wire: Use the correct gauge wire; using too small a gauge can lead to overheating and failure.
* Grounding: Ensure the heater system is properly grounded to prevent issues.
This is a general overview. The specific steps and complexities will vary depending on the exact condition of your truck and your existing heater system. If you lack experience, it's highly recommended to consult a repair manual and/or seek professional help. A poorly executed wiring job can lead to serious problems.
