[DeTomaso] Electrical Grounds, Volts of Confidence Modification, and Pantera Electricals

[F&D Terry]

Chris,

Thanks for posting your findings. The article I wrote for the POCA 
Newsletter explained that I had grounded each appliance too but I had 
not taken ohm meter readings. I only suspected there was a problem but 
never thought it to be as large as you determined. I feel the single 
ground wire arrangement presents a potential hazard to Pantera owners 
especially now that many are adding accessories with higher current 
demands. Nobody seemed to pay much attention to my article but your post 
may cause a few to modify their wiring for a safer environment.

I discovered the problem because my ground wire had a break in it before 
the fan junction. I don't know the cause of the break but the left 
parking lamp tried to seek a ground through the left headlight causing 
it to glow. Somehow current was routed through the windshield wiper 
motor, blowing the fuse. After regrounding everything, I never had any 
more trouble.

The single ground wire seems to be popular in Europe where many auto 
companies use a single ground wire. Here in America, we ground each 
appliance individually either through the devices' frame or a with a 
short pigtail. I'm sure this was started for economic reasons to 
conserve wire but it certainly works well.

Thanks again for posting your findings.

Fred T.

Chris Difani wrote:

>Guys:
>
>As some of you know, I'm in the process of rebuilding/restoring/going berserk/etc my '73L. Among the various changes I've made, one was implementing Mike Drew's "Volts of Confidence" "fix" for our "all the amperage thru the ignition switch" wiring system. 
>
>Now that takes care of the "plus" side of things. And I got to thinking about the "minus" side of things. I spoke with Fred Terry and I learned that the front half of the car is all grounded thru one very small stud under the dash. Essentially every electric appliance has a ground wire that runs back to that stud. And the ground wires aren't very big, and neither is that stud. Fred was very emphatic that if I did the "Volts of Confidence" modification, and then didn't add the individual grounds, I wouldn't be getting all the benefits that I should get from all my work. Fred had the tech logic and details for this, and was able to explain it to me in depth..(very smart guy).
>
>Okay, back to the Pantera. In the back half of the vehicle, every appliance is grounded right there, to the body, at the appliance. None of this "everything to one grounding bolt" concept. Why the front half is one way, and the back half another, I have no idea... 
>
>Okay, so now you ask why am I concerned about this?
>
>Glad you asked... I decided that what's good enough for the rear, is good enough for the front. Or at least I'd look into it with my trusty $17.99 on-sale-at-Harbor Freight digital multimeter... . 
>
>Since the radiator fans are a huge user of electricity, and a major element of our cars, I figured I'd check the ground question out by using them. I went to my radiator fans and using my digital multimeter, I measured the resistance from the negative side of the fan, to the body sheetmetal. This measurement is actually running from the grounding wire that runs from the radiator fan, thru the harness, and up under the dash, to that single stud, and then back to my meter's probe, which was "stuck" into the body sheetmetal. 
>
>This ohm reading was 8 ohms. That's 8.0 ohms. 8 point zero ohms.
>
>Then I spliced a 12 gauge wire into the black, ground wire, right at the fan's plug, and using a ring terminal, attached my new ground wire to the body sheetmetal, right there. I drilled a small hole, ran a carbon steel sheetmetal screw thru the ring terminal, and into the new drilled hole. Actually before I ran the screw in, I sanded the paint away from around the hole such that the ring terminal made solid contact with the bare metal. 
>
>Now I've got a ground wire that's right there! Right at the fan motor (well, almost- within 18 inches). I measured my resistance again from the negative side of the fan motor plug, to the sheetmetal body. This time I had 0.8 ohms. That's zero point 8 ohms.
>
>A decrease in resistance by an order of magnitude. This is very good. 
>
>With that kind of result, I then did the same thing to my other fan, and to every other major appliance in the front half of my car. It's simple to do, and makes a huge difference in the electrical efficiency of the system. In fact, I'd say that anyone that does the "Volts of Confidence" modification, and then doesn't do this, isn't getting all that they should from their effort and money.
>
>And that's my story... and I'm sticking to it...
>
>Chris
>
>Chris Difani
>'73 L #5829 "LITNNG"
>Sacramento, CA
>Email: cdifani at pacbell.net 
>
>
>
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