[sasilverbullet]

Why? I'm just wondering from an electrical point of view...I can understand for ease of troubleshooting why you would want one ground, but from a purely electrical standpoint, why?

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[flash]

varying ground potentials can easily lead to variance in voltage across the system - by tieing them all together, all circuits stand a better chance of having the same voltage - each time you tie a ground, you ahve a chnce of it not making good contact - a circuit will "seek" ground and it may not find it where you want it



from an audio perspective, this is essential - "ground loops" are noisy and ugly things - one of the first things we do when trouble shooting a system is re-route all ground to the same point - generally kills about 80% of audio ground noise we find

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[sasilverbullet]

Sounds reasonable...

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[Harvey]

Count your blessings and clean your grounds. The major culprit for electrical gremlins on the 928 usually has to do with a bad ground (many more than the 968 has). When buying a new Porsche, it's the first thing I do...cleaning up all the grounds. Just good insurance. Someday the 968s will be as old as most of the 928s and I think we'll be seeing similar problems, particulalarly if you drive in winter or rain. I even pull my fuses and reseat..as well as the relays and push wire connections. Better to do this in your garage than trailer your car later.



Harvey

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[Cloud9...68]

[quote name='mitch968' date='Jul 18 2005, 02:38 PM']Any tips for accessing the bellhousing ground point?  It seems really tight to get in there.

[right][post="7516"]<{POST_SNAPBACK}>[/post][/right][/quote]



Just a thought - Is the engine mount removal procedure, with its attendant lowering/raising of the engine, conducive to easier access to the bellhousing ground point? I'm planning to do my mounts this Fall, so I'm wondering. Thanks.

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[Brian]

i'm pulling this one out of the archives. hopefully someone will read it. <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

in the process of installing my new ice shark battery cables, i decided to clean up all the ground points. some were very difficult to access and i couldn't even find two of them.



could someone please enlighten me as to the location of gp i or vii in the rear? i found the one just to the left of the hatch mechanism where the hatch release motor ties in (and perhaps the taillights?). it's the one you use for a keyless system. i'm not sure if this is #i or #vii. but the other point back there.... i just couldn't find it. it was late and dark, so please be kind...



also, number ix and x. i found the major ground where the negative battery ties in. i'm guessing that this is x, right? then there should be one just foreward of that, but i couldn't find it? i did notice that there was a smaller wire also grounded with the large battery cable. does this jump up to anther point? i'm really hoping that it isn't under the manifold. i just don't want to remove that to clean a ground point!



thanks to anyone who takes a minute to help.



by the way, cleaning the gp's is time very well spent. everything is working better now. wipers, windows, gauges, inst lights. the only real bear was gp ii, which is actually two points under the fuse box!

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[sasilverbullet]

how do I get the fuse box off to get at those two grounds?

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[Brian]

there are two screws on opposite corners. they have a recess for a phillips head screwdriver, but also the shape of a sort of thumb screw. you unscrew them and just pull straight up on the box. there's some kind of clip molded in with the front of the fuse box. if you pull up on the box unevenly, you'll get it stuck. the screws are very long, so you don't have to pull them all the way out or worry about losing them. just loosen them up and leave them in their holes.

the wiring you'll discover under the fuse box is enough to make you dizzy. it's got some extra so that you can pull the fuse box out, but not too far. if you give the fuse box a half twist, you'll get a few more inches of slack (they've got the wire bundle twisted a turn or so to get them all to fit).

the ground points are toward the outside of the car - almost under the fender. they are upside down. i found one of them to be pretty clean and the other to be pretty dirty. they are the same size as all the other ground screws (i think 10mm?). i found a small box end wrench and a lot of patience did the trick. getting them out is a lot easier than putting them back in.

you may want to have your wife/kid/neighbor hold up the fuse box for a few minutes while you work on the ground screws. it's a little much to do by yourself - holding up the box and working on upside down screws that you can not even see.



another good one to clean is the one for the wipers. it's under the plastic beauty trim piece right in front of the windshield. that one was really easy to get to. it was a mess. my wipers work 100% better now.

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[Brian]

i don't know if anyone is into cleaning these ground points, but i thought i'd post just for posterity's sake i'd post an update.

i'm pretty sure that the ground point in the rear that i couldn't find before is actually under the car by the fuel filter. i saw it when i was changing the filter last night.

it was very dirty. i sanded it and re-installed it. not sure what it was grounding. maybe the fuel sender?

also, the other ground point at the rear of the engine block is right next to the main one from the battery to the block. i have no idea how you'd get to the bolt to clean it. it looked pretty clean so i just left it alone.



the only thing i can't seem to find, if it even exists, is a ground for the instrument panel. i'm guessing there's one up under the pedals, but i can't find it. i'd really like to because my gauges don't seem to work as well as they should, especially my gas gauge and my volt meter.



i will say this... my before and after from cleaning the ground points the second time around was .2 volts. i can't imagine what it was the first time! seems like a lot to me. i have an adjustable voltage regulator and i actually had to dial it down.

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[jww968]

I'm going from memory here (never safe) but on the 944 I believe that GP II was on the outer side of the footwell on the driver's side. Above the hatch release button in the area of the cruise control module. I assume it is the same for the 968.

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[Brian]

thanks jww.

i think you're right.



there are two ground points that are right under the fuse box/just under the fender. you can access them by lifting the fuse panel and reaching back under... or by crawling under the dash (ouch!). they're way up directly above the hood release lever.



after looking at it more closely, i think you're right - this is the grounding for the i.p. (and the fuse box). there must be 10 wires that all come together on 4 ring terminals there.



still can't keep my fuel gauge from slowly oscillating 1/4 tank up and down, but that must be another story...

probably either a bad gauge or a bad sender. not sure how to decide.

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