Routing a power wire through a firewall without protection is a major fire hazard. The vibration of the car will cause the sharp metal edge to cut through the wire insulation. A grommet slides into the hole first, providing a soft rubber cushion that wraps around the metal lip. The wire is then pulled through the center of the grommet safely. They are also used to seal out engine fumes and moisture. Use silicone spray to help slide wires through tight rubber grommets easily.
Mechanic Glossary
Grommet
A rubber or plastic ring inserted into a hole in sheet metal to prevent electrical wires or hoses from chafing against sharp edges.
Frequently Asked Questions
Measure the diameter of the hole in the metal and the outer diameter of the wire bundle. The grommet should fit tight in both areas.
Yes. If the wires are already installed, a split grommet can be wrapped around the wire and pushed into the metal hole.
Clean any oil or grease off the metal edge. The grommet groove must sit flush on the sheet metal to lock in place.
Standard grommets block splashes. For wet areas, use a liquid-tight wire gland or apply silicone sealant around the wire pass-through.