A bit more....
Car has sat with battery disconnected since Saturday and with a Fluke multimeter is showing 12.4V on its posts.
Disconnecting the only sizeable lead I could find on the alternator makes no difference to the current draw. None whatsoever - so I think that rules out the alternator as a cause. If, I've got the right cable that is - biggish one on the back of the alternator at the top that comes forward to a junction box mounted on the radiator fan upper shroud - yes?
Current draw is ever present - ie with everything that could be energised by the ignition key not. Next on my mind to check (as suggested) is starter motor cable. What might I expect to find? Conductive dirt permitting a path to earth? There's not much more that isn't switched via the ignition key to check. Three ciggy lighters in the front (maybe another two further back) and the interior lights (working fine). Double checked the interior lights - they all go out together and lights in sun visors also. All fused circuits have been checked - fuses pulled one by one. Any further suggestions anyone?
Power cable on the alternator should be pretty obvious. It's 6ga with a fusible link, should be connected directly to the positive battery terminal. The wire that goes over the fan shroud should be the main power for the engine fuse box, try removing that from the fuse box, and the power wire from the alternator. That should leave only the starter connected, if there's still a draw, then the starter is the issue, and you did the diagnosis without getting under the truck, double check your work by disconnecting the starter and checking the voltage, then adding the alternator power, check again, then add the fuse box and check yet again. Those should be the only the loads directly connected to the battery unless you have something aftermarket. If you do have something aftermarket directly connected to the battery disconnect that first, and check draw, as that's usually at fault. Motors and alternators can fail and draw current through the coils, best fix for that is rebuilding or replacing.
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