Mystery Wire?

[Seymour Snerd]

I already asked SPF this question and got an unhelpful answer, so I'm hoping one of you knows, most likely someone who did his own install:

On my car (P2160) in the wiring harness back by the battery there is a branch that contains two wires, 1 ~10 gauge red that goes to battery positive and supplies the 80A fuse (and therefore everything else but the starter and alternator), and a ~18 ga brown wire ~3/8" ring terminal.

I have hooked up my battery with the aforesaid red wire to +, and the chassis to -, and the small brown mystery wire open, and everything seems to work fine (lights, rad fans, tach, etc. etc.). So where does this small brown wire lead to? Being brown you would think it's for grounding something, but only if that something is a component I haven't tested.

Lynn's picture (the third one) at http://www.gt40s.com/forum/how-fueling-electrics/24132-spf-gt-wire-labels.html is different from the corresponding point in mine: he shows the red wire by itself and two light gauge brown wires which he labels simply as "battery negative". That unfortunately doesn't tell me what it does, even if it is in effect the same signal.

So does anyone know where in the schematic this small brown wire goes?

 

[Scott Calabro]

If no one comes up with the correct location via the prints, just disconnect the battery and start ringing wires with an Ohmeter.

 

[Randy V]

18g is pretty small...

Alarm system?
EFI - Keep Alive wire?

 

[Seymour Snerd]

If no one comes up with the correct location via the prints, just disconnect the battery and start ringing wires with an Ohmeter.

It's not on the prints.

Yeah, I could do that. I could try to access every single f----g wire termination in the whole car. The only way "just" belongs in that sentence is if you're goin to come over and do it for me. Have you ever tried to get access to the back of the instrument panel on an SPF?

I'm still interested in hearing from people familiar with the car though...

 

[Scott Calabro]

You gotta be kidding ... right?

How many circuits does the car have, 12?

You make it sound like you have to ring an L-1011!!!!

Here is a clue, Ohm the brown wire to chassis gnd....

 

[Kirby Schrader]

Mike Trusty put me on to these pictures. Maybe they will help you?

I already asked SPF this question and got an unhelpful answer, so I'm hoping one of you knows, most likely someone who did his own install:

On my car (P2160) in the wiring harness back by the battery there is a branch that contains two wires, 1 ~10 gauge red that goes to battery positive and supplies the 80A fuse (and therefore everything else but the starter and alternator), and a ~18 ga brown wire ~3/8" ring terminal.

I have hooked up my battery with the aforesaid red wire to +, and the chassis to -, and the small brown mystery wire open, and everything seems to work fine (lights, rad fans, tach, etc. etc.). So where does this small brown wire lead to? Being brown you would think it's for grounding something, but only if that something is a component I haven't tested.

Lynn's picture (the third one) at http://www.gt40s.com/forum/how-fueling-electrics/24132-spf-gt-wire-labels.html is different from the corresponding point in mine: he shows the red wire by itself and two light gauge brown wires which he labels simply as "battery negative". That unfortunately doesn't tell me what it does, even if it is in effect the same signal.

So does anyone know where in the schematic this small brown wire goes?

 

[Seymour Snerd]

Mike Trusty put me on to these pictures. Maybe they will help you?

Those are Lynn's pictures that I was referring to. Here's my version of his mystery wire in picture #3.

 

[Seymour Snerd]

You gotta be kidding ... right?
....
Here is a clue, Ohm the brown wire to chassis gnd....

I'm sorry, did I post this plea for useful information on the pissing-contest forum by accident?

 

[Rick]

I realize that to some, this may seem like rocket science, but indeed it's quite simple. the brown wire in your photo is the ground for the ECU. If you have fuel injection, it should be grounded to the neg. batt. post. Do yourself a favor and download the owners manual.

 

[Seymour Snerd]

Pricked by Mystery Wire

I realize that to some, this may seem like rocket science, but indeed it's quite simple. the brown wire in your photo is the ground for the ECU. If you have fuel injection, it should be grounded to the neg. batt. post. Do yourself a favor and download the owners manual.

Hey RC --

Yeah, most things seem simple when you already know. But bad documentation is rocket science, even for me. Thanks for the friendly help though. BTW I tried Scott's idea of "ohming it to ground" and since it's open that really illuminated the situation a lot. I guess I'll ground it to one of my carburetors.

BTW, how did you get SPF 2080, the negative 20th car built? Do they pay you to take one that early?

 

[Mike Christian]

Alan,

There is more than one serial number string of SPF available. One series starts 20XX and the other starts 21XX. The 20XX are set aside so that owners can replicate a specific original serial number car - they pay a premium.

Mike

 

[Scott Calabro]

Re: Pricked by Mystery Wire

BTW I tried Scott's idea of "ohming it to ground" and since it's open that really illuminated the situation a lot. I guess I'll ground it to one of my carburetors.


Well now you can keep ringing wires then eh?

Nice atitude to boot.

Must be a heavy flow day.

Note to self... Don't try to help SPF owners.

 

[Rick]

Re: Pricked by Mystery Wire

Hey RC --

Yeah, most things seem simple when you already know. But bad documentation is rocket science, even for me. Thanks for the friendly help though. BTW I tried Scott's idea of "ohming it to ground" and since it's open that really illuminated the situation a lot. I guess I'll ground it to one of my carburetors.

BTW, how did you get SPF 2080, the negative 20th car built? Do they pay you to take one that early?

Hey Einstein,
I hope you didn't hurt yourself trying to figure out how SPF numbers their chassis. Like the wiring, it's quit simple. It appears you need to conserve your mental capacity to try to finish your assembled, wired, painted and upholstered roller or pay someone that knows what they are doing, to do it for you.

 

[Jack Houpe]

Re: Pricked by Mystery Wire

Note to self... Don't try to help SPF owners.[/QUOTE]

Come on dude, I like your posts.

Alan put the brown wire to the negative side of that dry cell rechargeable you got in the battery box and all will be OK.

 

[Seymour Snerd]

Re: Pricked by Mystery Wire

Must be a heavy flow day.

Note to self... Don't try to help SPF owners.

Maybe it's reproductive. I think it's just witty repartee.

Anyway, Scott, please don't take it out on the other SPF owners. With one exception (so far), the others seem to be good guys.

 

[Seymour Snerd]

Re: Pricked by Mystery Wire

Hey Einstein,
I hope you didn't hurt yourself trying to figure out how SPF numbers their chassis. Like the wiring, it's quit simple. It appears you need to conserve your mental capacity to try to finish your assembled, wired, painted and upholstered roller or pay someone that knows what they are doing, to do it for you.

I would, but I paid so much for my serial number I can't afford it.