Funny how that works. Just yesterday my glow plug relay light was intermitently working, and then finally just quit. I immediately suspected one or more glow plug(s) failure. Popped the cap off of the relay just to see if all looked normal, and there was a tiny fracture in the 80 amp strip fuse. I pushed the two pieces of the fuse together, and instantly the glow plug light resumed working, just like nothing ever happened. I ordered a new one this morning in Fastlane, it was like $1.47. So, in my experience, with my car (1983 300TD wagon), no 80 amp strip fuse, no glow plug light.
