Trunk Mount Batt. Opinions needed

Oh, not any of this circled as well.

View attachment 1715599751

That should be simple to check and way easier with two people. "At some point" you need to read voltage drop with one probe stabbed DIRECTLY into the top of the battery POST

As I said, 'a long wire' from front to rear for your meter. "I forgot" you can jumper the starter from the trunk this makes things easier.

So: GROUND test. Connect meter to good body ground, like trunk latch. Stab second probe into the battery NEG post. Jumper Ford relay crank engine, read meter. Post reading

Hot side tests:

Same as above. Stab one probe into battery POS post. Clip other meter lead to engine side of Ford solenoid. Crank and read, post reading here

Next, take your long extension wire, clip to the Ford solenoid on engine side. Go up front, hook meter to extension wire, and clip other meter lead to starter main post. Crank and read.

Engine GROUND. Clip meter to good body ground and to engine block. Crank and read

All of the readings down to this point should be VERY low, the lower the better. THEY ALL ADD UP and that is the drop in the system.

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A backup test "sort of" tells you same thing:

Clip meter to starter and engine block, crank and read. Absolute minimum is 10V the higher the better