My 83 300SD glow plug light stopped working about a week ago. 2 days ago I replaced all 5 glow plugs with new Bosh glow plugs. I checked the 80A fuse in the glow plug relay box, it tests ok. I also checked for continuity of the glow plug wiring going from the 5 prong cap to the end of each individual wire. They all test ok. I checked the glow plug light bulb in the cluster, it is good. Still the glow plug light does not come on (but my car starts absolutely beautifully). Is there anything else I can check? Any suggestions?
Any help is much appreciated.

Thanks

Lodester