Sierra 2500 HD; Diesel. Sierra 3500 HD; Diesel. Silverado. A Relay for the window defroster. Accessory Delay Relay. Color-Black. Diesel Glow Plug Relay. Relay for Accessory power. Starter Relay. Accessory Delay. Accessory Power. Diesel Glow Plug. Starter. Window Defogger. Window Defroster. Included with: Fuse & Relay box, Fuse & Relay box Order by application, Fuse & Relay box Order by description.