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Old 04-06-2003, 08:47 AM
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Question Grounding Strips vs Frame

I was reading something the other day that said grounding to the frame only provides 16% ground and the best way to ground everything is to run a full-size battery ground wire to 3 separate grounding strips : one in the rear, one in the interior, and one in the engine section ...

Opinions?

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Old 04-06-2003, 09:27 AM
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Well this is a tricky one cause I hate to comment on something I have not read myself. As far as grounds go a general rule of thumb is good grounds can make or brake an electrical system. Running heavy gauge battery cable through the entire car with grounding strips would certainly do a great grounding job, but do you really need it? Even on the newest cars with multiple computers running things and many many accessories manufactures do not do this, think of the manufacturing cost and bulkiness of it. Most evrything is still grounded to the body with sheetmetal screws or to the frame. I always make sure my cars a good ground cable to the engine block, another from the neg. post to the body/frame, and another ground strap from the rear of the engine to the firewall. I would have to question that 16% ground theory cause as part of most of the pinpoint tests that I perform on a regular basis one of the most common tests is checking the ground side of a circuit. If I had to guess I would say that most peoples electrical problems are a result of poor connections (rust, loose wires) or just bad wiring jobs. If you can post that article that would be great to read.


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Old 04-06-2003, 10:03 AM
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Wire size determines capacity, your %16 ground figure would refer to that. Sure the ground strap is only capable of carrying %16 of the load since nothing in the interior of the car draws that much anyway. There is no need to have big cables grounding various parts of the chassis unless a component of the car is grounded on that feature and it draws a lot of power. The starter is the heaviest power draw on the battery and consequently has the largest ground connection, what's in the interior that grounds to the battery? The heater fan? That's peanuts in the grand scheme of things. Put a big amp in the trunk and you better provide a low resistance ground or you face power losses caused by low capacity wiring if you ground to the trunk floor. Your grounding straps must reflect the load of all the components attached to that part of the car or you will have problems.

A bigger concern is ground loops caused by poor connections and multiple ground points with various resistance and capacity values at the connections points. Wire size only determines capacity. Ground loops are the concern.

Does this make sense? <img src="confused.gif" border="0">
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Old 04-06-2003, 10:15 AM
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[quote]Originally posted by 4 Jaw Chuck:
<strong>Does this make sense? </strong><hr></blockquote>
No, now get out of here!

j/k Sorry chuck, couldn't resist.

[quote]you face power losses caused by low capacity wiring if you ground to the trunk floor. <hr></blockquote>
So I guess that 24 gauge speaker wire I used to ground my 500watt amp is a nono???


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Old 04-06-2003, 03:10 PM
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The source for that "16% ground" info wasn't an article, but rather the new Wire Works catalog I just got in the mail. If you have a copy, the info can be found on page D-1, where they're selling grounding kits. Duh!

Quote : "The steel frame rail is a poor conductor of ground current since it only conducts 12-16% of copper. Connections to the frame rail will rust over a period of time causing grounding problems!"

PS - I plan on using Di-Electric grease on each and every connection (I'll be doing my EZ-Wire kit in a week or two) and I doubt rust can occur with that protecting each connection.

It sounded like a scare-tactics/sales pitch to me, but I wanted to get some opinions.

Thanks, guys.

Alan
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Old 04-06-2003, 03:27 PM
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[quote]It sounded like a scare-tactics/sales pitch to me <hr></blockquote>
Funny, even scare tactics usually have a certain amount of truth in them . While copper may very well be a better conductor than steel I definately say they are blowing things just a bit out of proportion. There are thirty year old cars on the road right now that have using their body/frame as a ground path since day one. Like 4-Jaw said, no matter what you use as a ground path just make sure any wires or straps you use are a sufficiant size. You don't want to run 13amps through a 24 gauge ground wire. Is that smoke I smell?

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Old 04-06-2003, 03:59 PM
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i'd think measuring the resistance between the negative battery terminal and certain points on the frame would indicate how good the ground is at those points.

if i measured under one ohm from the neg terminal to the part of the frame in question, i'd consider it to be a pretty good ground. makes sense doesn't it?

4 jaw, i've heard of ground loops, but thought they were only of concern for the noise they created in stereo components. do ground loops have negative effects on other accessories?
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Old 04-12-2003, 03:09 AM
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DMorris right on concerning poor grounds being root of electrical problems. Ron Francis Wire Works instructions address frame grounding in reference to trunk battery installations. Grounding to frame results in poor performance. Being a little dence at times, I made the short ground to the frame and ground the frame to the starter bolt, both with #2 wire. Guess what? Erratic starting problems and radio on/off cycling until I ran the number 2 wire all the way to the starter bolt. I did leave the frame ground strap on because numerous other items are grounded to the frame.

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Old 04-12-2003, 04:51 AM
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I agree with dmorris, the article you read almost sounds like they were wiring a fiberglass car the needs grounds run everywhere. On a metal car only a good 2-3 gauge strap to engine and 1, 10 ga. to the body works great. Usually you don't have to run one to the frame because of all the contacts with the frame. Granted lots of rubber mounts but lots of contacts, too! Voltage drop tests can be run on grounds, too. So you can tell if a frame strap is needed.
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Old 04-12-2003, 10:17 AM
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Man, you guys are the best -- thanks.

My truck's battery is under the floor on the passenger side (just in front of the seat). There's a ground strap from the negative post of the battery to the frame ... then, on the other side of the firewall in the engine area, theres another ground strap from the frame to the engine.

I guess this is a cool setup because the truck starts like a champ ... even though there's a ton of corrosion on both battery posts and the ground strap to the frame looks like hell.

The only thing I'm thinking of adding (when I do my EZ-Wire kit) is a #2 wire to the firewall - and, of course, a new ground strap and a new battery.

Alan

[ April 12, 2003: Message edited by: horvath ]</p>
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Old 04-12-2003, 11:34 AM
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Just put a honda civic hatchback in your trunk and ground every thing to it. Take the spoiler off though, or you might not have room for the spare tire.
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Old 04-12-2003, 03:57 PM
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Good idea! THEN I'll have traction when it snows, too!


Alan
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Old 04-16-2003, 03:00 PM
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[quote]There's a ground strap from the negative post of the battery to the frame ... then, on the other side of the firewall in the engine area, theres another ground strap from the frame to the engine. <hr></blockquote>

I couldn't tell from how you wrote whether or not you have a ground cable from the battery post directly to the engine block/starter bolt. The other grounds are needed but for the heavy current draw of a starter I would have a heavy gauge battery cable going from the battery negative post directly to the engine block/starter bolt.


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Old 04-16-2003, 08:28 PM
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Thanks, dmorris1200

This has been on my mind ... I know the ground from the battery post is best going to the engine block/starter bolt, but my battery is not in the engine compartment as is usually the case. It seems, in 1954 anyway, Chevy put a battery compartment/box on the frame under the floor on the passenger side and the ground wire goes to the frame about 12" from the battery. There's an access door on the floor that provides entry to the battery area.

When I got the truck that was the only grounding situation there was. I figured the ground was too far from the engine block to go direct, so (on the other side of the firewall, about 2 feet away) I put another ground wire from the frame to the engine block -- both are brand new ground wires (the flat woven type).

Would you suggest I rearrange this set up? I mean, would it be better to run the ground to the engine block/starter bolt even though I have to run a much longer ground cable?

PS - My positive wire is 36" ... and goes from the battery post to the starter.

Thanks.

Alan

[ April 17, 2003: Message edited by: horvath ]</p>
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Old 04-17-2003, 06:11 PM
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I would try and run a ground cable from the engine block directly to the neg. battery post if you can snake it along where the positive cable runs. I would do this only because of the amount of current draw needed to turn over the car. This may also help you with the corrosion problem. Keep the existing grounds hooked up as well for the rest of the electrical. Good luck .


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