[DeTomaso] pantera electricals

[Chris Difani]

Lee:

When you look at the actual wiring harness, there's a bunch of connections 
within the ground wire "stream", as they all lead back to that one stud. 
They have enough "add ons" that the measurement isn't "just the wire", it's 
the wire plus. Plus a lot of terminals and connections within that harness. 
In places it's reduced from 6 wires down to 1 wire, and then after 5 or 6 
feet, and umpteen more ground wires joining the "stream", it's reduced 
again.... and so on. The grounds start at the driver's side 
headlight/parking light, crosses over to the passenger side headlight, then 
back thru the fender to the horns, wiper motor, parking light, then from the 
fuse panel, up into the dash, and all that "stuff" until it finally wanders 
to that single ground stud. Even a single oxidized or corroded 
splice/connection within that circuit can create the resistance I measured. 
And my car's pretty clean. No rust, or other problems in it. I'd hate to 
think what some of these cars have inside their wiring harness... could be 
really scary.

As you say, the wire itself probably isn't the culprit here... it's all the 
"extras" that have been added into the mess. I suspect that if the factory 
had left each appliance grounded separately, all the way from the load to 
that under dash stud, the resistance wouldn't be nearly as much as what it 
is. Also keep in mind that those connections, within the "ground wire 
stream" have 35 plus years worth of oxidation, corrosion, and/or other 
metallic deterioration.

Which is why the resistance drops so dramatically when all that "other" 
resistance sources are removed from the circuit.

Which is also why it's such a good idea to install individual grounds for 
each appliance.

Chris

Chris Difani
'73 L #5829 "LITNNG"
Sacramento, CA
Email: cdifani at pacbell.net




----- Original Message ----- 
From: "Lee Farrell" <lee_farrell at sbcglobal.net>
To: <detomaso at realbig.com>
Sent: Wednesday, May 30, 2007 3:35 PM
Subject: [DeTomaso] pantera electricals


> chris, you are measuring something other than wires.   a 10 foot long,  14 
> guage wire has a resistance of about 3 tenths of an ohm.  even 0.8 ohms is 
> a lot for car power wire.   at 8 ohms and 12 volts, your fans would only 
> get 1 - 2 A, versus a requirement of probably over 15 amps.  My car had 
> the original, single-pink-to-the-front wiring, and with the original fans, 
> I measured a few tenths voltage drop (at the fans) when the fans turned 
> on.   So even the poorer version of the original wiring costs you less 
> than 5% loss, and shows the original circuit resistance is way less than 1 
> ohm (I don't know the exact current draw of the fans).     That said, 
> there is no good reason to ground the fans with the 
> mystery-black-wire-to-the loom.  Lee
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