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1975F 100 302 automatic. This is my daughter's truck.
She failed inspection for some reverse light issues. The truck sat at her house for about two weeks. I went to get it and the battery was dead. I started charging the battery, when I did, I noticed smoke underneath the hood. I disconnected the jumper cables and found that the wiring harness from the alternator to the voltage regulator to the solenoid were fried. Luckily that was the extent of the damage.
I have a few wiring harnesses From 1973 to 79 trucks I have parted out. I installed a new (used) harness. Once I start the truck I test the:
the battery with the engine running, it shows 12.99 V.
the alternator with the engine running I get 13.29 V.
with the truck running, the field terminal on the voltage regulator I get 11.4 V.
I always thought charging was about 14 V. Am I missing something?
Last edited by benbuilder; Sep 1, 2021 at 10:30 AM.
Reason: misspelled word
Did you check at idle or with rpms up a bit?
Check battery volts with engine off. Then start and check at battery with rpm around 1500-2000 and see what you get. I like to see at least 14.4 and/or up to 14.8
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