well ive managed to finish my 200A alternator project, but it seems that i might have a bad ground in the cab as an added bonus.

If i measure the voltage at idle on the batteries, i get a nice 14.3v
my tech1a however is reporting 13.1v

i suspect a resistive ground to the pcm, and gauges, but i have no idea where these circuits are grounded..

also, my hvac fan dies, i had to run an independent ground to the body to get it running again..

anyone have any ideas where to look?

Vin

The main body ground is between the firewall and the passenger-side rear of the head, also where the main PCM harness grounds are bolted to the intake manifold.

Also check the main harness where it crosses the ac pipe in the lower firewall.

Place your DVM black lead on the neg battery post, then the red lead on the engine block, the body, and etc - a voltage reading at any juncture will indicate poor ground connection in between.

something along the same lines, that I have been wondering. Does the PCM case share the ground of the PCM itself? Meaning, would it be useful to run a ground from the body to the metal PCM casing?

dont for get to also look at the pos side of the circut i have changed many inj switches on these trucks to solve problems. they use points 6 of them when they get burned they dont deliver full power. use a volt meter from the pos side of bat to the pos wire of any thing that you are having a problem with if the reading is more than .50 than that item isnt getting full power. same test can be done with neg side just switch to neg side of bat and neg of item.
any voltage that you see doing this test is voltage that the wiring is not delivering.