Electrical Ground Locations

[bpossel]

We always seem to focus on the famous open paintless area that resides under the radiaitor overflow tank (ground location).

As I took apart my car for the upcoming repaint, I located many more ground locations that I wanted to share.  This is important to help resolve electrical ground issues...

Below Overflow Tank & Under Aux Fusebox Bracket
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Firewall (Main Engine Ground)
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By Windshield Washer Pump (on body post)
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Inner Dash behind Key Starter
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Left Rear Behind Quarter Pannel Trim
Download Attachment: LeftRearQtr_a.jpg
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Right Rear Tail light is grounded also
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Headlight Buckets
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bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[doitwright]

I found these numerous ground points while detailing my engine compartment. I found some round stickers in my kids craft drawer.  Prior to painting, I sanded the area around the ground point then placed a sticker over the hole.  The stickers are removed after painting leaving a nice round area around the ground connection.  After the wires are reconnected, I plan to apply a clear coat over the remaining exposed bare metal to prevent it from rusting.

Frank Koronkiewicz
Willowbrook, Illinois

1970 280SL Light Ivory

[ja17]

Hello Bob,

Good documentation! Maybe we can get the "weep holes" (water drainage) points in the body and chassis documented also!  I know there are several in each rocker panel, one in each headlight bucket, some on the floor pans, and some under the hood.  These should be checked to make sure they are not plugged up.

Joe Alexander
Blacklick, Ohio

[bpossel]

Hi Joe,

Will do...
Bob

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[wbain]

I hate that there are so many ground points on these cars, my 220S included as well as my W126's. There can be allot of current flowing through the chassis to the main battery ground. That can't be good. Does anyone have an opinion on rust and current flow through the chassis?

Thanks

Warren Bain 1965 220S, 1989 300SE, 1989 420SEL, 2002 Ford Crown Vic Police Interceptor

[Peter van Es]

Bob, keep up the good work... look at how I've shamelessly stolen    your stuff for the Technical Manual.

The more you post (like the hole locations) the better the Technical Manual becomes.

http://www.sl113.org/wiki/pmwiki.php?n=Electrical.Ground

Peter

Also known as 'admin@sl113.org' and organiser of the Technical Manual (http://www.sl113.org/wiki/pmwiki.php). Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280SL.

[Peter van Es]

quote:Originally posted by wbain

I hate that there are so many ground points on these cars, my 220S included as well as my W126's. There can be allot of current flowing through the chassis to the main battery ground. That can't be good. Does anyone have an opinion on rust and current flow through the chassis?

Warren, basically all the current used will flow through the chassis back to the -ve battery terminal. How much that is, and whether that is bad, depends on what's happening. During starting a lot of current will flow, and when you have all the lights on, too.

Measure the voltage at the terminals of your battery when the car is off, and when it is running. That'll give you much more of an indication of whether you have problems. Typically, if your battery does not deplete, you are allright.

When rust enters in the circuit, it will create higher resistance (it acts as a less than perfect conductor). That means you will see a (larger) voltage drop when the car is running. However, since the chassis often has non-rusty areas that current can flow through (essentially the resistance of the rust is in a parallel circuit with a less resistant part) the effects are typically quite limited, except in specific areas (e.g. when a light has a ground wire connected to a rusty chassis part).

Peter

Also known as 'admin@sl113.org' and organiser of the Technical Manual (http://www.sl113.org/wiki/pmwiki.php). Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280SL.

[bpossel]

Hi Peter!

Thank You! You are ahead of me...  I was going to put this in the wiki manual over the holidays when I have some "down time" with my car being over at the bodyshop.  Thanks for adding it.

I am very have to contribute and help in any way.

Kind Regards,
Bob

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[wbain]

Thanks Peter,

I just wonder how much rust is being created by current flowing through various welded joints and overlapped seams. I'm planning on consolodating my ground points and wiring them together into a U shape, not a circle. 12 GA copper solid wire should work well.



Thanks

Warren Bain 1965 220S, 1989 300SE, 1989 420SEL, 2002 Ford Crown Vic Police Interceptor

[al_lieffring]

quote:Originally posted by wbain

Thanks Peter,

I just wonder how much rust is being created by current flowing through various welded joints and overlapped seams. I'm planning on consolodating my ground points and wiring them together into a U shape, not a circle. 12 GA copper solid wire should work well.



Thanks

Warren Bain 1965 220S, 1989 300SE, 1989 420SEL, 2002 Ford Crown Vic Police Interceptor

Warren

For as long as there has been electrical components attached to automobiles there has been the false rumor that body corrosion is caused by the electrical current of the battery flowing through the body. This is pseudo-science that sounds good but isn't really true.

There have to be three things present for a galvanic reaction;
two (2) dis-similar metals
an electrolyte solution (acid or alkali)
and an electric current.

If this were in-fact the cause of body rust, the most body corrosion would be where the copper wires attach to the iron body.

Even if these elements were present it still would not cause any damage to the spot welds because both pieces involved are the same iron alloy, and the current carried through any one point of the body is almost immeasureable.

Over the years there have been Flim-Flam devices that usualy had a wire that went to the front and another to the rear of the car and were supposed to produce a "protective" counter-current. The sales pitch was that car makers knew this "secret" but didn't use it because they wanted your cars to rust away so you would need to buy new ones.
But of course all they really were was a box with a red light that blinked every 5 minutes and bilked $29.95 plus shipping and handling from hapless car owners.

Al Lieffring
66 230SL

[seattle_Jerry]

ummmm steel chassis, aluminum doors and acid rain :twisted:

1967 230SL Havana Brown Auto with A/C