Sometimes it's the battery (system) even when the battery is fine. My son spent something like $1200 chasing the ghosts of electrical issues in a Ford Expedition with multiple mechanics. And they did in fact replace the battery at some point in there, to no avail.
It turned out that one of the battery _cables_ was bad; enough corrosion had built up under the insulation that the voltage would do all kinds of strange things depending on the exact load on the system. $20 for a new cable fixed it all.
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Sometimes it's the battery (system) even when the battery is fine. My son spent something like $1200 chasing the ghosts of electrical issues in a Ford Expedition with multiple mechanics. And they did in fact replace the battery at some point in there, to no avail.
It turned out that one of the battery _cables_ was bad; enough corrosion had built up under the insulation that the voltage would do all kinds of strange things depending on the exact load on the system. $20 for a new cable fixed it all.
I had the same problem after refueling once. Car had been running fine for hours and suddenly would not start
Turned out to be a bad ground connection. Fixed it on the spot with a wire brush to remove the corrosion and rust.