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

Thu May 31 11:19:48 EDT 2007

Regarding the braided cable, Napa has a nice piece for about $12. Item#:
PHI9150

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470
<http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=PH
I&PartNumber=9150&Description=Battery+Cable+Grounding+Strap>
&LineCode=PHI&PartNumber=9150&Description=Battery+Cable+Grounding+Strap

Indy 

Dave

-----Original Message-----
From: Mark McWhinney [mailto:msm at portata.com] 
Sent: Wednesday, May 30, 2007 10:32 AM
To: 'Chris Difani'; detomaso at realbig.com
Subject: Re: [DeTomaso] Electrical Grounds, Volts of Confidence
Modification, and Pantera Electricals

Hi Chris,

The problem with the single stud is not so much that it is too small but

that it is a single point of failure and is rather hard to get to.  As the

stud gets gunked up over the years, many strange things start to happen.

The single stud also requires long ground wires, some with multiple

connectors.  It is a messy and error prone design.

My aftermarket fans are already grounded locally.  When I was shooting my

radiator fan problem, one of the first things I did was a continuity check

on the ground wires.  I do not recall the resistance measurement, but it was

something well under 1 ohm.

Cleaning that one stud and locally grounding the major current suckers

should keep your cat purring.

BTW, on the back end of the car is a braided cable that runs from the back

of the ZF to the body.  It carries the current from the starter to the

ground.  Modern folk lore says that it is not enough cable for the current.

Some people have added a second cable that runs from the engine block to the

body.  I added one, but did not see an obvious change.  YMMV.

-----Original Message-----

From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On

Behalf Of Chris Difani

Sent: Tuesday, May 29, 2007 9:45 PM

To: detomaso at realbig.com

Subject: [DeTomaso] Electrical Grounds, Volts of Confidence Modification,and

Pantera Electricals

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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