Glow plug light didn't light up. Tried to start and she wouldn't fire. Turned the key a couple of times, the light lit up, went out per normal and she fired up.

All 5 glow plugs are 3 months old. Other than checking connections and the 80 amp fuse, could this be my GP relay on the fritz. How do I check it,,,,,,,I am a complete moron when it comes to electrical stuff and how to use a voltmeter.

PS, it is the original GP relay, 1977 300D.

TIA

JCD