Check your alternator output at idle with the glow relay off or disconnected. I had a lot of strange no crank, low charge issues that turned out to be a weak battery and multiple Bosch voltage regulators.

Regulator wasn't regulating, battery wasn't holding a charge but seemed to take a charge. I ended up replacing the battery and scalping a regulator from a parts car.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.