The Ford Barn

JtownJoe · 05-17-2010, 09:43 PM

Help with tracing electrical short. I have a slow drain on my battery with all systems off. I have installed battery cut off but I would like to find & eliminated the problem. No lights or ignition, coil, points & etc are staying on (small needle movement is showing on amp. gauge) short occurs as soon as positive cable is connected to the starter terminal. I traced it up to the firewall terminal box and eliminated any shorts in the dash components so I am thinking it is somewhere in the bowels of the wiring harness, any suggestions to help find it? I have a voltage meter that beeps when hooked up between the negative battery cable & the starter terminal but not sure how to isolate from there.

JtownJoe · 05-17-2010, 09:45 PM

sorry, "as soon as negative battery cable is connected"

TK in LA · 05-17-2010, 10:04 PM

Might try pulling the light switch off the bottom of the steering column. That will eliminate anything in the light and horn circuits. If that isn't it it's a matter of pulling one circuit or wire at a time till you find it.
Good Luck and let us know what you find.

Kurt in NJ · 05-17-2010, 10:34 PM

Try unhooking the cutout --it could be sticking, or if you have an alternator try unhooking that. --most anything else will either light up, or burn up the wire --shorts in wiring harnesses usually make smoke.

Tom Wesenberg · 05-17-2010, 10:35 PM

Is the termianl box a repro? I've heard some of them have the 2 terminal screws that can touch the firewall and short out.

If you connect the voltmeter between the battery post and disconnected battery cable you should measure no voltage. If you measure voltage just start looking at the different circuits for a short to ground. Do you have an original popout switch?

Are you using an alternator?

Mike V. Florida · 05-17-2010, 10:41 PM

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Tom Wesenberg · 05-17-2010, 10:47 PM

Mike, that's probably the best schematic I've seen for the Model A.

They even show the inside of the coil, which no one would take apart and work on, so I wonder why they didn't show the inside of the horn, which is something that one would work on. Thanks, Tom

JtownJoe · 05-17-2010, 10:52 PM

Thanks for suggestions, will try & report back. JOE

05-17-2010, 09:43 PM	#1
JtownJoe Senior Member Join Date: May 2010 Location: Johnstown, PA Posts: 342	wiring problem Help with tracing electrical short. I have a slow drain on my battery with all systems off. I have installed battery cut off but I would like to find & eliminated the problem. No lights or ignition, coil, points & etc are staying on (small needle movement is showing on amp. gauge) short occurs as soon as positive cable is connected to the starter terminal. I traced it up to the firewall terminal box and eliminated any shorts in the dash components so I am thinking it is somewhere in the bowels of the wiring harness, any suggestions to help find it? I have a voltage meter that beeps when hooked up between the negative battery cable & the starter terminal but not sure how to isolate from there. Last edited by JtownJoe; 05-17-2010 at 09:44 PM. Reason: typo

05-17-2010, 09:45 PM	#2
JtownJoe Senior Member Join Date: May 2010 Location: Johnstown, PA Posts: 342	Re: wiring problem sorry, "as soon as negative battery cable is connected"

05-17-2010, 10:04 PM	#3
TK in LA Senior Member Join Date: May 2010 Location: La Verne, Ca. Posts: 826	Re: wiring problem Might try pulling the light switch off the bottom of the steering column. That will eliminate anything in the light and horn circuits. If that isn't it it's a matter of pulling one circuit or wire at a time till you find it. Good Luck and let us know what you find.

05-17-2010, 10:34 PM	#4
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,155	Re: wiring problem Try unhooking the cutout --it could be sticking, or if you have an alternator try unhooking that. --most anything else will either light up, or burn up the wire --shorts in wiring harnesses usually make smoke.

05-17-2010, 10:35 PM	#5
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: wiring problem Is the termianl box a repro? I've heard some of them have the 2 terminal screws that can touch the firewall and short out. If you connect the voltmeter between the battery post and disconnected battery cable you should measure no voltage. If you measure voltage just start looking at the different circuits for a short to ground. Do you have an original popout switch? Are you using an alternator?

05-17-2010, 10:41 PM	#6
Mike V. Florida Senior Member Join Date: May 2010 Location: South Florida Posts: 14,054	Re: wiring problem Sponsored Links (Register now to hide all advertisements) __________________ What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II

05-17-2010, 10:47 PM	#7
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: wiring problem Mike, that's probably the best schematic I've seen for the Model A. They even show the inside of the coil, which no one would take apart and work on, so I wonder why they didn't show the inside of the horn, which is something that one would work on. Thanks, Tom

05-17-2010, 10:52 PM	#8
JtownJoe Senior Member Join Date: May 2010 Location: Johnstown, PA Posts: 342	Re: wiring problem Thanks for suggestions, will try & report back. JOE

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