Where is my brain box hot wire ?

Cummins Conversion & Builds

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Where is my brain box hot wire ?

Postby jethro » Mon Sep 07, 2015 10:44 pm

I am trying to get the big parts plumbed up on the cummins/f-350.
Got the water and air tubes done and in. Now rigging the battery cables up.
Got the starter wires found. One thing I have not been able to identify yet-
is how the brain box gets its 12 volt power. I have an unknown black wire which
comes out of the big main bundle near there. It looks to be about a 1/4 inch thick wire with a round
ring eye on the end. could this be it ????
I have not been able to find that area on the schematics in my Haynes manual.........
Any thoughts ?

Tim
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Re: Where is my brain box hot wire ?

Postby PToombs » Tue Sep 08, 2015 4:08 pm

Are you talking about on the Ford harness?
pete

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Re: Where is my brain box hot wire ?

Postby jethro » Tue Sep 08, 2015 7:08 pm

Thanks for the reply pete-
Yes- the ford harness. I have leafed through every page of the Haynes schematics - and I don't see any where it shows
the ecm. I no longer have the ficm- it is separate from ecm in fords from what I have learned (youtube)
There MUST be somewhere there a positive 12 volt supply wire which supplys power to the computer (ecm?)
that controls all the cabin functions and the non-fuel injection functions in the engine compartment. I have lots of
square plugs in the engine bay where engine stuff once plugged into- and then a single fat wire with a ring eye on the end.
(looks to be about a 4 ga. stranded- a small cable)
The main harness bundle comes through the firewall near the brake master cyl. and then down onto the top of the inner fender
- and there a bunch of things are terminated with square plugs (now open). This is about where this small cable exits the harness. This is about the same general area as where the ecm is . (the ecm now only has 1 of its 3 cables connected-
assuming the other 2 were to old motor or injection computer)

I have the huge battery cables in now which run from battery to starter- but I have not determined how to (where) to get power to the rest of the chassis and ecm.
I may try calling ford-cummins tomorrow- they may know---- (?)

Tim
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Re: Where is my brain box hot wire ?

Postby jethro » Tue Sep 08, 2015 7:46 pm

Found this just now -
http://www.motorcraftservice.com/vdirs/ ... rsion1.pdf

Schematic showing the PCM pinout and what all the cables run to-
this may help some- but doesn't answer the question directly though.......
The diagram shows about 6 or 8 places where +12 volts goes- but you would think that they enter somewhere from the battery from a single conductor- maybe running to the engine fuse/rely box maybe ??????

Tim
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Re: Where is my brain box hot wire ?

Postby Gots_a_sol » Tue Sep 08, 2015 7:58 pm

There is a junction stud on the drivers inner fenderwell that your heavy wire might go to but I dunno if the newer truck has that or not though.
-Joe

00 Excursion - 12v/nv4500, he351cw, 5x12s, 366 spring, THD piston pump, 4" intake/exhaust
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Re: Where is my brain box hot wire ?

Postby PToombs » Wed Sep 09, 2015 4:33 pm

No problem Tim. I don't know crap about fords wiring, but sometimes by posting something others get excited and will have an answer for you. ;)
pete

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Re: Where is my brain box hot wire ?

Postby jethro » Wed Sep 09, 2015 10:01 pm

I have been studying the thing a little-
Appears that there should be a wire from the battery- through a fusable link- and then go to the main bus strip
in the cab fuse box- where most things are fused and power then distributed. There must be a wire coming out of the
fuse box going into the harness bundle that goes through the firewall which is the one which gets +12 volts from the battery.
I just don't see a wire like that coming out of the harness up on the inner fender well where the harness wires all split off.....

may have to pull out the fuse box a little and see if I can guess which wire it might be. might guess it could be the fattest wire ?????

might take brute electrical force ( I hate that ! :-) )

Tim
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Re: Where is my brain box hot wire ?

Postby jethro » Wed Sep 09, 2015 11:09 pm

YEAAAAHHHHHHH !!!!!!
just figured it out.
I google searched pictures of the battery cables. Noticed that the ford cables (both positive terminals) have a #10 stud built
onto the clamp/terminals. I was suspecting that one of these studs might mount the power wire in question. The Ford-cummins guy said it should be a red wire. Couldn't ever find a red one. There were only 2 loose wires with ring eyes.
One was yellow and I believe that was to the starter solenoid. The other was a black cable. right size but wrong color.
So I went out and looked to see if the black one reached to the battery. It did. It had ribbed plastic protective wrap over
it. I had peeled it back a little and it showed black. Un-taped the wrap and peeled it back more- the black underneath was electrical tape- it was a BIG RED WIRE ! Looks like that must be it !

Tim
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Re: Where is my brain box hot wire ?

Postby PToombs » Thu Sep 10, 2015 4:36 pm

See, when in doubt, peel it out! hahahahaha 8)
pete

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