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  #11  
Old 05-27-2013, 10:33 AM
BillsCamino BillsCamino is offline
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Gotta disagree Hank...

Engine sits on rubber mounts...trans mount is rubber too.
I've seen quite a few tranny rear output shaft bushings ATE up trying to provide an electrical ground.
Engine requires a good CHASSIS ground...not just the small one provided indirectly by the neg battery cable.
Found this out years ago....on a '69 Elky. This car would loose power every time the clutch was pushed in. Valve cover ground cured that problem.
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  #12  
Old 05-27-2013, 12:33 PM
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Hank70SS Hank70SS is offline
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Well you can look in the factory assembly manual Bill, U63 Radio-Ground Straps. Two with an AM radio and a 3rd one with an FM radio. What you call the 'small' cable coming off the negative battery cable is 10g, same size as the pigtail coming off the positive battery cable. So if the positive pigtail can supply all the power needed the negative can supply the ground for that power. GM figured that was enough to carry the load for all lights and accessories. The starter is a different story and why the main cables go directly to the starter and engine.

I can show you 10 cars without those braided cables for everyone that has them. Those braided cables were never meant to be current carrying. Their electrical theory was a little messed up but they felt the braided cables would help suppress the electrical interference from the ignition. If they were meant to carry current one regular insulated wire would have been sufficient.

Like I said, if adding those grounds solves a problem then you have a problem with the chassis ground elsewhere.
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  #13  
Old 05-27-2013, 01:34 PM
BillsCamino BillsCamino is offline
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Respectfully, I guess we'll just have to agree to disagree.

My original BAL built '66 300 DeLuxe, 6 cyl w/PG. has a braided ground from rear most valve cover bolt to firewall. Also has a braided ground from lower pass inner fender to frame.
NEVER had any radio....
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  #14  
Old 05-27-2013, 01:53 PM
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Hank70SS Hank70SS is offline
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Quote:
Originally Posted by BillsCamino View Post
Respectfully, I guess we'll just have to agree to disagree. ....
Respectfully, no problem Bill.
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  #15  
Old 05-28-2013, 07:38 AM
JD3426 JD3426 is offline
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Bill & Hank,
I have had no luck finding the problem so far but still looking. As far as the ground in question. My '72 came with an AM radio and has never had one. Never a problem until recently, if adding the additional ground strap solves it I guess I will be happy but also wondering what I am misssing ? I did discover yesterday that the horn is not working, dont regularly use it so am unsure when that issue started or is it is related.

Thank you both for the help.

Jim
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  #16  
Old 05-28-2013, 02:38 PM
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There are multiple ground straps on the rad core support. Headlights, voltage regulator, etc. Make sure all those are good clean solid connections. You may also want to invest in a multimeter so you can check voltage. Harbor Freight has one for 6 or 7 bucks. Not the best quality but good enough for occasional use. I would check voltage in interior of car, fuse box is good location, while idling in park then after shifting into gear. If lights dim and voltage stays pretty constant then it would be a grounding issue. If voltage drops significantly, several volts, then more likely a charging system or positive wire issue. I would want to know which one so you know where to start looking

There are 2 sides to the equation. Positive from the battery to fuse box then lights or other accessories. The other side is grounding through the chassis back to the battery. All lights and accessories are grounded to the chassis.

As far as the horn, pull the wire from the horn then take a jumper wire from horn connection and touch to battery positive post. This will at least tell you if the horn works. Have someone push the horn button and listen to the horn relay, you should be able to hear a click in the relay when the button is pushed. This is another good place to use a multimeter. Meter between wire from horn relay going to horn and a good ground. When the button is pushed you should read over 12v on the wire.

Let us know what you find out then we can give you more ideas on where to move to next. It's a process of elimination when troubleshooting electrical problems.
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  #17  
Old 05-28-2013, 07:12 PM
JD3426 JD3426 is offline
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Hank, thanks for all the help. I have to be out of town for a while but will report back as soon as I have tried your suggestions.
Thanks again, Jim
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  #18  
Old 05-28-2013, 07:44 PM
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Wish you were a little closer, I'd be glad to help out. Don't think we have any other members close to you. Good luck, let us know what you find and maybe we can provide some help.
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  #19  
Old 07-14-2013, 07:49 PM
JD3426 JD3426 is offline
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I finally found time to dig into this again. The horn relay connections just needed cleaning, there are 12v + at the fuse box, drops to 10v when moving from one gear to another @ idle. Any ideas where to look next ?
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  #20  
Old 07-15-2013, 07:04 AM
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Hank70SS Hank70SS is offline
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Where does the voltage drop occur? Does it also drop at the horn relay? How about at the junction block by the battery. If you know where it starts it makes it easier to find the problem. Could be corrosion where the the forward light harness plugs into the bulk head connector, or at the main splice near the horn relay or the horn relay or the junction block.
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