Replace the battery, Autozone has them cheap for $69 and they work just fine. Check the ground and clean the connections.

Replace the glow plugs, again Autozone has Bosch ones for $10 each.
Replace the 80 amp strip fuse. If it breaks you lose the glow plugs it is right behind the drivers side headlight in the black box. $.30

Replace the alt, I'd use a Bosch rebuild Fastlane could hook you up.

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2006 CL500
2009 C300 4matic
1969 280SE
2023 Ram 1500
2007 Tiara 3200