I haven't heard back from you about Bartamos' test #3 which tests the switch making electrical contact with the starter motor. Sometimes the heavy copper lugs in the switch fail to make contact with the copper lug on the starter due to wear, corrosion or simply from linkage wear.

Actuate that button on the starter switch by hand. If the button is depressed fully and the starter motor does not spin effortlessly under this no-load condition, then you have a starter switch/starter problem.

~~ Jethro
1954 3100
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