Quote:
Originally Posted by Grandma’s 68
I can see the logic that the alternator wired to the starter post that is connected to the battery basically ‘shorts’ out the rest of the power circuit. It’s all still live and current flows to the devices but not much to cause a differential over the ammeter. Basically negligible flow across the ammeter, so not moving.
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Yes, having the alternator output re-routed to the starter batt stud still results in a fully functional charging system. But the altered current path prevents the ammeter from working as intended.
Quote:
Originally Posted by Grandma’s 68
I tried a quick test by cutting the alternator wire at the starter and jumping it to the ‘correct’ location at the b/w fuse.
However it doesn’t look like I’ve got any change in ammeter results. I get about 0.17A between black and b/w wires. That about the same as before (0.22A). Now that may be coincidence, so is it normal operation of the gauge basically sitting in the middle with a fully charged battery and functioning alternator? Is 0.2A flow what to expect?
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Yes, it's normal for the gauge to stay at (or close to) the middle with a fully charged battery.
Quote:
Originally Posted by Grandma’s 68
I also noticed that the ‘shunt’ wire that goes along the front of the truck looks a heavier gauge. Is the ‘shunt’ wire some sort of special wire?
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No, the shunt wire isn't anything special. Just regular stranded copper automotive wire. The gauge and length of the wire does determine it's resistance so if it has been replaced with something other than the stock equivalent, it might alter the sensitivity of the meter. For example, a heavier gauge wire will have less resistance (for an equivalent length) so a greater majority of the current will go through the shunt and less through the meter, making it less sensitive.
Quote:
Originally Posted by Grandma’s 68
I may still rehash the wiring to get it like the original diagram, but I’m curious now to functionally test the gauge and would appreciate some guidance on how it’s supposed to look under normal charging and how to simulate alternator failure.
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It is normal for the needle to be toward the charge side (especially after the battery has been discharged a little by starting up the engine). The exact amount of deflection will vary depending on the battery's state of charge. As the engine runs and the battery charges, it's normal to see the needle slowly return back to (or close to) the center.
To simulate an alternator failure, simply leave the engine off and switch on some loads (like the headlights, heater fan, wipers, etc.) ... that should cause the needle to swing toward the discharge side. And more load should result in more needle deflection.