P11 full rewire

[wolk625]

Hey guys, 

 

Been lurking for a while, and finally have some time to really give my car the attention it deserves. First up on my list to redo is to address the original wiring - although still mostly functional, I'd like to replace it all with some nice new braided wire before finishing off the interior, and was wondering if anyone else here has a ballpark idea of how much (length) of wire I'm looking at to order? I have the schematic from the service manual but it doesn't seem to mention length anywhere. Also, where are some critical areas where I should consider adding or replacing body grounding straps? Thanks in advance.

 

(P11 business coupe, still original 6V)

[Young Ed]

Can't really help with lengths but on my 48 I upgraded all the 16g wire to 14. I feel its helped my lights be as bright as possible. 

[Doug&Deb]

Rhode Island Wiring and YNZ Wiring both offer complete harnesses. They look correct and have all the correct connectors.

[wolk625]

Thanks for the sources, definitely sounds like the easier route to go. I think I'll still call or email them regarding the specifics on their kits, like if they include the dome light and tank sending unit wiring, and what gauge they're using where. I might also just buy some extra grounding ribbons and start going to town strapping all body panels together.

[jeffsunzeri]

Ground straps:

1. Engine to frame.

2. Engine to firewall.

3. Body shell to frame.

 

[Sam Buchanan]

How 'bout just battery ground to engine and battery ground to body? Won't that cover it?

 

(I hope it does.....that is all my car has as far as I know and everything works perfectly....)

Edited September 18, 2019 by Sam Buchanan

[Los_Control]

33 minutes ago, Sam Buchanan said:

How 'bout just battery ground to engine and battery ground to body? Won't that cover it?

 

(I hope it does.....that is all my car has as far as I know and everything works perfectly....)

 

1 hour ago, jeffsunzeri said:

Ground straps:

1. Engine to frame.

2. Engine to firewall. 

3. Body shell to frame.

I think what Jeff is sharing, is what is common on a modern car. I personally think is a great idea. Especially with a older 6 volt system, there is no such thing as too much ground.

Only thing I would add, on my pilothouse, the battery is under the floor and grounds directly to the transmission. And the only current ground. And it works.

Back in 1948, we did not even run ground wires in our houses. Through evolution, we learned and evolved ... ground is good.

So you ask if this is original, probably not, Would I add it to my car? Yes.

 

I personally would have no issue seeing decent ground wires on any show car, just a peace of mind on my own car.

But proven to work without.

 

[Eneto-55]

2 hours ago, Los_Control said:

Back in 1948, we did not even run ground wires in our houses. Through evolution, we learned and evolved ... ground is good.

 

In the interior of Brazil, there is often only a single electrical wire run.  You get the ground from the, well, the ground.

 

But in relation to our cars, since I will be rewiring my P15 anyway, I am inclined to run an extra wire to like the headlamps, for the ground (rather than depending on all of the sheet metal connections, especially with painting all of the separate panels before assembly).

[Los_Control]

I just think the extra connections today, are from past experience of failed connections of yesterday.

 

My post states I only have 1 ground connection from the battery to the transmission. And it works.

But if that connection fails, I have no backup.

I Think but do not know, that the extra grounds added to cars were for a backup in case the original failed.

Rust and corrosion can cause the failure ... but if you have a few connections, not just one wire will leave you walking.

 

adding extra grounds to the wiring, kinda like adding disk brakes. Not original but it is better. You need to decide what level of restoration you want to achieve.

[Sam Buchanan]

3 hours ago, Los_Control said:

I think what Jeff is sharing, is what is common on a modern car. I personally think is a great idea. Especially with a older 6 volt system, there is no such thing as too much ground.

 

I wonder if the additional grounds in modern cars may be due to the dependence on digital CAN buses multiplexing throughout the entire vehicle.

 

 

Edited September 18, 2019 by Sam Buchanan

[Los_Control]

6 volt positive ground, a large amount of solutions to a fix for what ever issue ... is a better ground.

Bad lights or slow cranking ... first thing to check is the ground.

Why not just eliminate that option?

 

And this is the last time I will post in this thread.

My opinion is more ground is better, do whatever you think works for you.

[pflaming]

On my 53 Suburban I used a harness from EZ Wiring..  it is a good product. But should I ever rewire an old vehicle again, I would get a  time. Would take no more than two days. Kits have many more wires than what is required. 

JMHE. 

[T120]

From my own experience - I bought an old 1930's Chrysler car several years ago.The car started fine and I checked it over as best I could at the time of inspection..  I didn't bring my trailer and the seller wanted the car moved right away, I  arranged for local storage.I went back a month later to pick up the car and the engine wouldn't turn over, (foot starter).I removed the front seat and found the connections at the battery were clean.I found a local shop that sold 6 volt batteries of sufficient capacity to start the car. I purchased one and  installed the new battery - still no joy on operating the starter.I was in a hurry to get the car home .While I don't recommend this procedure ,observing battery polarity, I used jumper cables from my truck (12 volt) directly to the starter motor and engine block and the car started right up.The first thing I did when I got the car home was to replace the battery cables with proper gauge cables.In this vehicle the ground is connected directly to the transmission and it was in very poor condition.In short there was nothing wrong with the starter motor, the problem was a very poor cable and ground connection at the transmission.

So I would agree with, "Los_Control" and others that good ground connections are important...

Edited September 19, 2019 by T120

[pflaming]

If memory serves me right, the frame is the return route for the current to circle. If for example the bed on a truck is NOT grounded to the frame, the  tail lights will not work. That means the cable to the battery from the engine carries a lot of energy. Now that means the engine must be grounded to the chassis so all those electrical items are also grounded back to the battery. 

 

 

[Sam Buchanan]

1 hour ago, T120 said:

 

So I would agree with, "Los_Control" and others that good ground connections are important...

 

I think everyone on this thread agrees that good grounds are very important. 

[James_Douglas]

I used Paul Little of Harnesses Unlimited for the restoration (Concourse) of the 1949 Desoto Convertible.

 

The work was very good and I had little trouble using his kit. The one thing I did that was not stock was to run a set of #10 green wires from the headlight cans (I used a long machine screw that went through to the inner fender and used a ring terminal) to the positive cable at the battery. I had the cables made and the #10 wires were crimped with the actual round wire in the lug.

 

I also run a small ground strap from one of the engine side of the motor mount bolts to the mount side. I also run the factory ground from the engine to the fire wall.  Lastly, I run a ground at the rear of the frame to body. 

 

I think the direct ground from the bucket to the battery makes a large difference in the voltage delivered to the headlight. 

 

James

 

[chrysler1941]

On 9/17/2019 at 11:52 PM, Doug&Deb said:

Rhode Island Wiring and YNZ Wiring both offer complete harnesses. They look correct and have all the correct connectors.

 Definitely  the easiest way. Done many car wiring and this also cheapest in the end.

 

On 9/18/2019 at 8:10 PM, Sam Buchanan said:

How 'bout just battery ground to engine and battery ground to body? Won't that cover it?

We've covered it before, yes probably on a factory new car with rust-free frame, new copper wires and hardware, fresh battery etc ?

 

On 9/18/2019 at 9:00 PM, Los_Control said:

Especially with a older 6 volt system, there is no such thing as too much ground.

100%

 

On 9/19/2019 at 12:02 AM, Sam Buchanan said:

I wonder if the additional grounds in modern cars may be due to the dependence on digital CAN buses multiplexing throughout the entire vehicle.

Yes but CAN bus system do not use "frame" for signal circuit. They have different their own "ground" as a different ground potential (zero reference) The lack of metal in modern cars and sensitivity of digital signals calls for additional ground shielding. 

 

So here is a quiz question for the forum. ? Why where older vehicles positive grounded ? And shouldn't we be grateful ??

[Los_Control]

6 hours ago, chrysler1941 said:

So here is a quiz question for the forum. ? Why where older vehicles positive grounded ? And shouldn't we be grateful ??

I blame the small block chevy engine.

 

Not sure if chevy every had a positive ground car. while most all car manufacturers did use positive ground.

Some claim that the positive ground helps prevent rust, Not sure if there is any significant difference there. If true we should be grateful 

My Uncle told me this was true, there seems to be some scientific facts to back it up.

 

But for the sake of everybody to be consistent with each other, we needed to go one way or the other, not both.

And GM seemed to be the big kid on the block at the time, they were not going positive ground. So everyone else went negative ground.

Even though positive ground was reported to be better.

Again the GM analogy comes from my Uncle, but it made sense to me.

 

 

[chrysler1941]

17 hours ago, Los_Control said:

I blame the small block chevy engine.

 

Not sure if chevy every had a positive ground car. while most all car manufacturers did use positive ground.

Some claim that the positive ground helps prevent rust, Not sure if there is any significant difference there. If true we should be grateful 

My Uncle told me this was true, there seems to be some scientific facts to back it up.

 

But for the sake of everybody to be consistent with each other, we needed to go one way or the other, not both.

And GM seemed to be the big kid on the block at the time, they were not going positive ground. So everyone else went negative ground.

Even though positive ground was reported to be better.

Again the GM analogy comes from my Uncle, but it made sense to me.

 

 

Your uncle is right. 

Current flows from positive to negative. Voltage in the reverse direction, from negative to positive. 

 

Positive ground, has negative voltage on the wires, and protected the copper and electric components, frame connectors from corrosion. This is referred to as cathodic protection. sacrificial anode being the vehicle frame itself.

Ever wondered how switches and electrics "generally" always work on older cars, and not on cars from 60-80s. 

Edited September 22, 2019 by chrysler1941