crazy flashing of Seat Belt and Glow Plug lamps
 

300SD, 424,000 miles. All is great, but I am now seeing random flashes from the seat belt warning light, after a day or two of that the glow plug light started randomly flashing while driving.
I am guessing there is a solid state module somewhere that controls the timers on these lights and it is dying.
Anybody know what it is called, where it is, how to repair or test?
Thanks!

I just had the same problem. My buzzer would come on too, unless I was buckled. My problem was with the glow plug relay. I had a relay from a 603 in my 617. You probably don't have the same relay as I did. Just letting you know what fixed my blink problem.

Your relay was from a 602 not a 603 matt. I'm glad that fixed it though