Desperatley need help with electrical fault

[koolkatsmoke]

So first let me apologize for making this more confusing than what it has to be... I have a mayor electrical fault that seems to be coming from the interior cab and unable to find or narrow down to the culprit.
Got off work one morning and went to start ST and all seemed good when key in but when i went to start it, it went dead and wouldn't turn over. First thought was battery, checked terminals and tried to jump it with a coworkers car and still would not turn over. Managed to get ST started by push starting it and made it home this way. I had the battery tested and is good, so i then figured it would be starter or solenoid related. Replaced with different starter and solenoid and still no go, dead in water. Pulled out meter and realized that with leads disconnected my battery reads 12.6v but as soon leads connected it drop to 6v and below then slowly comes back up to 12.6v. Began testing fuses and all are good, disconnected alternator and starter and still voltage drop still present. Started to pull fuses one by one in the engine distribution box and fault is coming from the #1 fuse that leads to the fuse panel.
Nothing inside performs or lights up and i have a mayor chatter from the relays that are on the lower right driver side (flasher relay block). All the fuses are good in the panel and removing one by one by one didn't help a bit to narrow down where the fault may be. Removing fuse #25 which says its cluster/GEM makes the relay chatter go away but does not aid in the fault. Any kind of action still creates the voltage drop (tapping on brakes or locking/unlocking doors). I have traced and removed all external connectors to brake lights and still drop is present.
I have the Hanes manual and it has helped me at times before however the wiring schematics are not very good and do not show for this particular model just in general. I have tried to trace the wire back from the distribution box to the cabin but loose it in the firewall and unable to find it in the interior of vehicle. As it stands i have removed the radio and bezel, instrument panel, door panel, ignition switch and all connectors, GEM, brake light connectors and have tested all relays and replaced hazard relay and still voltage drop is still present.
I am out of ideas and direction in which to continue, thus why i am pleading for any Ideas or help that can aid. An actual wiring schematic (engine and/or interior) for a 2003 ST 2wd manual tranny would be a great help since i am doing the tracing old school wire by wire since the manual doesn't help and unable to trace or loose the main wire at the firewall.
Ive looked thru so many topics and as of yet have not found one that resembles the issue that im going thru.
Sorry for making this so long but thought id try to describe my issue as much as possible. Thanks for all ur help in advance and for taking the time to read thru all of this.

 

[bdmaash]

..................... Pulled out meter and realized that with leads disconnected my battery reads 12.6v but as soon leads connected it drop to 6v and below then slowly comes back up to 12.6v....................................

could be an old weak battery, when you first hook up the battery, the current draw will be high, until it figures itself out, the current draw goes down - (the slowly comes back up).

pull the battery and get it load tested

 

[koolkatsmoke]

thx for ur reply.
I did have the battery removed and tested at a local auto parts and it tested good. test readout showed 12v @ 900cca.

 

[bdmaash]

thx for ur reply.
I did have the battery removed and tested at a local auto parts and it tested good. test readout showed 12v @ 900cca.

Was the load test done after you measured the battery dropping to 6V?

There is draw when the battery is connected initially, but it's well under 10A I would say maybe under 1A (I've never measured it). That means the capacity of the battery is very low if it drops to 6V during initial hookup then it recovers to 12.6V.

It could be a combination of the alternator not being able to supply enough current to run the truck and charge the battery at the same time, and also a degrading battery.


pull the alternator and get that load tested.

Check to make sure all grounding wires (straps) are good and not corroded at the connections in the engine bay.

 

[ncranchero]

Still sounds like a bad battery. Do you get a strong arc (blue) when reconnecting the battery? You can expect a small yellow arc but if you're not gettong a good POP when you connect it I'll still go with the battery being bad. Maybe they tested it incorrectly. you describe a bad battery.........

 

[koolkatsmoke]

Still sounds like a bad battery. Do you get a strong arc (blue) when reconnecting the battery? You can expect a small yellow arc but if you're not gettong a good POP when you connect it I'll still go with the battery being bad. Maybe they tested it incorrectly. you describe a bad battery.........

Well that was it afterall. I feel like a retard since this was my gut feeling all first. But i did remove the battery after noticing the drop and had it tested at Advanced Auto Parts (sorry don't mean to site another place, just want people to know what useless motherloving tools really are). They told me the battery was good and even gave me a printout showing it rated at 900cca. Well after tracing everything and yes i mean everything, all connectors, all fuses, all relays and bulbs (just in case),distributor box and fuse panel, pretty much eliminated everything and verified all good even wiring. With my own doubts and ur suggestions i got myself a battery load tester and sure enough dead, dead, dead.
This is partly my own stupidity for believing in a yahoo over the counter that i really dont know his expertise (sorry no offense to those of you who do this for a living) just this particular store. Ive been burned by this before and it just chaps my ass.

NCranchero thanks for ur PM response and link, ive seen those here and there and have always wanted to get one, but until now really never had the need until now. Thought it would have been better to have an electronic copy than a hard copy. But im in the process of ordering should it be required, better to have and not need, than need and not have.

Guys thanks so much for your responses, i thought i was missing something that i haven't checked yet, but really just my own common sense.
you guys have been a mayor help and im back upo and running.
thanks again

 

[ncranchero]

Bad batteries/low voltages play havoc with these trucks !! Glad it was simple to repair.