Finding Existing Grommets:
The safest and easiest method is to utilize existing grommets or holes in the firewall. These are rubber or plastic seals designed to allow wires and cables to pass through while maintaining a weathertight seal. Examine the firewall carefully, both from the engine bay and the interior. Look for:
* Factory Grommets: These are the ideal option. Often you can carefully enlarge a small existing grommet with a slightly larger drill bit (being very careful not to damage anything on either side) or use a slightly larger grommet if you find a suitable size.
* Unused Spaces in Existing Grommets: Sometimes a grommet already has wires passing through, leaving space for additional wires. You can carefully add your wires alongside the existing ones.
Creating a New Passage (Use Caution!):
If you can't find a suitable existing grommet, creating a new one is riskier and requires more care. Here's what to do:
1. Plan Carefully: Determine the precise location where you'll drill. Avoid drilling into anything crucial like brake lines, fuel lines, or the HVAC system. Consult a wiring diagram or service manual to identify critical areas.
2. Use a Small Drill Bit: Start with a small pilot hole and gradually increase the size to accommodate your wires. This minimizes the risk of cracking the firewall.
3. Install a Grommet: Once the hole is the appropriate size, install a rubber or plastic grommet to protect the wires and maintain a watertight seal. These are readily available at auto parts stores.
4. Protect the Wires: Use split loom tubing or electrical tape to protect the wires from abrasion against the firewall's edges.
Common Entry Points (Proceed with Extreme Caution, Verify Location First!):
Some common, but not guaranteed, areas where people have routed wires in Cavaliers include near the master cylinder, brake booster, or along the sides near the HVAC system. Again, thoroughly investigate before drilling. Improper drilling can lead to significant damage.
Tools You'll Need:
* Drill with various sized drill bits: Start small!
* Grommets: Get the appropriate size to fit your wires and the hole.
* Wire loom/split loom tubing: To protect your wires.
* Electrical tape: To further secure the wires.
* Safety glasses: Essential for protecting your eyes from debris.
* Shop manual or wiring diagram: This is crucial for identifying safe areas and understanding the existing wiring.
Important Considerations:
* Consult a Repair Manual: A factory service manual for your 1999 Chevy Cavalier is highly recommended. It will show you the firewall's construction and identify potential hazards.
* Safety First: Always wear safety glasses when drilling.
* Weatherproofing: Ensure a good seal to prevent water ingress.
* Grounding: If you're adding a ground wire, make sure it's properly secured to a clean, bare metal surface on the chassis.
Remember, this process carries inherent risks. If you're not comfortable performing this task yourself, it's best to consult a qualified mechanic. Improperly routing wires can lead to electrical shorts, damage to the vehicle, and even safety hazards.
