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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / October 2005Grounded circuit troubleshooting
I have a 71 Opel GT with a dead short in the instrument panel lunination circuit. What is the best way to isolate the ground as it seems that everything is tied together into one big mess. Are there any free internet sites that explain basic ammeter use and trouble shooting of grounded circuits. My experiance with meter use is none and would like to learn more in this area. Thanks A test light can be used. It's simpler and cheaper, just a light bulb with two wires comming from it. Touch the wires to two pices of metal and if a current is flowing it will illuminate the bulb. > I have a 71 Opel GT with a dead short in the instrument panel lunination > circuit. What is the best way to isolate the ground as it seems that [quoted text clipped - 4 lines] > > Thanks -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned opps, should have also mentioned a test buzzer. same as the test light but it makes a sound which is sometimes better when working in places where you can't see. > A test light can be used. It's simpler and cheaper, just a light bulb with > two wires comming from it. Touch the wires to two pices of metal and if a [quoted text clipped - 14 lines] > homepage: www.ncf.ca/~ag384/top.htm > warning: non-FreeNet email must have "notspam" in subject or it's returned -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned >A test light can be used. It's simpler and cheaper, just a light bulb with >two wires comming from it. Touch the wires to two pices of metal and if a >current is flowing it will illuminate the bulb. If there is a voltage differential between the two pieces of metal touched with the probe wires, then a voltage differential will be displayed. Example: 1 wire is at 100 volts the other wire is at 300 volts what do you think you will read between these wires if these wires are in an open circuit? The answer is: between eachother, 200 volts between100 volts and earth ground or neutral safety bus, 100 volts between 300 volts and earth ground or neutral safety bus, 300 volts This has nothing at all to do with current. There can be zero current flowing in the wires, and you will still measure this voltage. Amperes is the unit of measurement for current. What if -both- wires are alive with 300 volts? What will you read? ZERO VOLTS if you just put your probes on the two wires, each carrying 300 volts! IOW, if you don't know what you're doing, DON'T DO IT. Lg >> I have a 71 Opel GT with a dead short in the instrument panel lunination >> circuit. What is the best way to isolate the ground as it seems that [quoted text clipped - 4 lines] >> >> Thanks Ageed, for sure!! >>A test light can be used. It's simpler and cheaper, just a light bulb with >>two wires comming from it. Touch the wires to two pices of metal and if a [quoted text clipped - 39 lines] >>> >>> Thanks Wow..... Are you two fools for real? It's an old 12 volt car with a short..... What's he gonna do, blow a fuse? LOL! Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 http://www.imagestation.com/album/index.html?id=2120343242 (More Off Road album links at bottom of the view page) > Ageed, for sure!! > > [quoted text clipped - 45 lines] > http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups > ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- >Wow..... > [quoted text clipped - 3 lines] > >What's he gonna do, blow a fuse? LOL! What he can do is melt a wire, or an entire wiring harness, allowing a lot of current to flow through it while trying to find a short. At least, that's what I did when I was eighteen and stupid. (It did turn out, though, that the insulation was all turning to goo and I had to rewire the whole car anyway.) --scott  Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >>Wow..... >> [quoted text clipped - 3 lines] >> >>What's he gonna do, blow a fuse? LOL! ======================================================= >What he can do is melt a wire, or an entire wiring harness, allowing a lot >of current to flow through it while trying to find a short. There's your answer *Wise Guy* Lg ======================================================= >At least, that's what I did when I was eighteen and stupid. (It did turn >out, though, that the insulation was all turning to goo and I had to rewire >the whole car anyway.) >--scott AC OR DC??????? >>A test light can be used. It's simpler and cheaper, just a light bulb with >>two wires comming from it. Touch the wires to two pices of metal and if a [quoted text clipped - 38 lines] >>> >>>Thanks >AC OR DC??????? Bob told me you're both. >>>A test light can be used. It's simpler and cheaper, just a light bulb with >>>two wires comming from it. Touch the wires to two pices of metal and if a [quoted text clipped - 38 lines] >>>> >>>>Thanks Your uncle? >>AC OR DC??????? > [quoted text clipped - 42 lines] >>>>> >>>>>Thanks >Your uncle? I want you to tell me, in simple terms, what makes *you people* think you know more about this *stuff* than a 60 year old guy who has been doing this stuff for over 1/2 Century. This rock-headedness of *YOUR GENERATION* is the reason 2,000 Service People have come back from Iraq dead-in-the-box. Your arrogance is going to get you KILLED some day. It's just a f.cking shame I won't be there to see it happen. Lg >>>AC OR DC??????? >> [quoted text clipped - 42 lines] >>>>>> >>>>>>Thanks > >Your uncle? > > I want you to tell me, in simple terms, what makes *you people* think > you know more about this *stuff* than a 60 year old guy who has been > doing this stuff for over 1/2 Century. Because the 60 year old guy is mentioning 300 volts where there isn't any. > This rock-headedness of *YOUR GENERATION* is the reason 2,000 Service > People have come back from Iraq dead-in-the-box. It's _your_ generation that put them there is the first place. > Your arrogance is going to get you KILLED some day. It's just a > f.cking shame I won't be there to see it happen. If you're nice to people, maybe they'll take pictures and send them to you... You People?? Just who do you think you're talking to, and just how do you place ME into "YOUR GENERATION"? I would wager to you that I am closer to your generation, than the generation you place me into. You my friend are the one who sent this thread of into a tangent. Just how do my two posts of 5 words total, cause you to relegate me to "YOUR GENERATION"? My post of AC or DC was a valid query, since though the discussion centered on automotive systems (which would seem to indicate DC), we were also talking up to 300 volts, well beyond what would be commonly found in automotive systems. Differential voltage measurements between two AC voltages bring into play a plethora of variables that the casual observer would'nt anticipate. KenG >>Your uncle? > [quoted text clipped - 56 lines] >>>>>>> >>>>>>>Thanks >You People?? Just who do you think you're talking to, and just how do >you place ME into "YOUR GENERATION"? I would wager to you that I am [quoted text clipped - 9 lines] > >KenG See this part here...: ================================================================ I have a 71 Opel GT with a dead short in the instrument panel lunination circuit. What is the best way to isolate the ground as it seems that everything is tied together into one big mess. Are there any free internet sites that explain basic ammeter use and trouble shooting of grounded circuits. My experiance with meter use is none and would like to learn more in this area. ================================================================ This OP has ZERO knowledge and/or experience with using a multimeter, yet he is intent on troubleshooting a low voltage HIGH CURRENT problem. Have you ever shorted the B+ on a fully charged battery to the Ground terminal? Be sure to use a nice thick WRENCH because a good part of it is going to be welded, and another part of it vaporized, just before battery EXPLODES spewing hot acid everywhere. Now that is what fuses are for, but they aren't worth a sh.t as you and I know, when circuits don't use them because of a short somewhere. So we are talking about the potential of realeasing an Electrical Bomb here, and you want to f.ck around with nomenclature. I told the OP stay away. Don't do it. And you can go back to sleep. Lg > This OP has ZERO knowledge and/or experience with using a multimeter, > yet he is intent on troubleshooting a low voltage HIGH CURRENT > problem. Have you ever shorted the B+ on a fully charged battery to > the Ground terminal? Dash lights are hardly "HIGH CURRENT." As was mentioned by another, the OP merely needs to substitute a 12 volt bulb (#194 in a holder) in place of the fuse that keeps blowing, when the 12 volt bulb is no longer illuminated, he's found the short to ground. > My post of AC or DC was a valid query, since though the > discussion centered on automotive systems (which would seem to indicate > DC), we were also talking up to 300 volts, well beyond what would be > commonly found in automotive systems. Consider that, if "one" doesn't know how a 1971 Opel is equipped, "one" may be including the possibility that the OP's vehicle has an electric or hybrid powerplant (~300V DC in the storage batteries). Consider also that "one" doesn't know much - but talks alot. Toyota MDT in MO >> My post of AC or DC was a valid query, since though the >> discussion centered on automotive systems (which would seem to indicate [quoted text clipped - 7 lines] > >Toyota MDT in MO Innuendo doesn't suit you fuckstick. I presumed you were more of a Man than that. My mistake. Lg >>> My post of AC or DC was a valid query, since though the >>> discussion centered on automotive systems (which would seem to indicate [quoted text clipped - 12 lines] > > Lg I'm impressed at how quickly you figured out who he was talking about. Even though it was obvious to most, I figured it would be over your head. Bob > You People?? Just who do you think you're talking to, and just how do > you place ME into "YOUR GENERATION"? I would wager to you that I am [quoted text clipped - 9 lines] > > KenG You forgot high frequency and whether it's single phase of three phase... 8-) > I have a 71 Opel GT with a dead short in the instrument panel lunination > circuit. What is the best way to isolate the ground as it seems that > everything is tied together into one big mess. Are there any free > internet sites that explain basic ammeter use and trouble shooting of > grounded circuits. My experiance with meter use is none and would like to > learn more in this area. Dead short meaning you blow the fuse every time you turn on the lights? As others have suggested, use a test light or buzzer, but wire it to *replace* the fuse that keeps blowing. That will keep the current down to a reasonable level, as it has to go through the test light before the short to ground. Remove every bulb that the circuit runs (I've seen bulbs where the filament supports inside have fused, causing a short), and if the test light is still lit, move on to the wiring, looking for frayed connections, insulation that's rubbed off where it goes through bulkheads, etc. > Dead short meaning you blow the fuse every time you turn on the lights? > [quoted text clipped - 6 lines] > move on to the wiring, looking for frayed connections, insulation that's rubbed > off where it goes through bulkheads, etc. Far and away the best advice given up to this point. Good job, MB. Toyota MDT in MO > I have a 71 Opel GT with a dead short in the instrument panel lunination > circuit. What is the best way to isolate the ground as it seems that [quoted text clipped - 4 lines] > > Thanks Do not use an ammeter- use an Ohmmeter. These are part of what is called a VOM, or today more likely a digital multimeter. I don't know of any specific sites for using them, but I'll bet a good google search would find some. Also, many libraries have books on using such meters. If I had posted the question I'd be pretty confused by now. So maybe go to the public library and get a book on car repair and look in the electical section. I have copies of second hand basic maintnenance and repair manuals, including the Dummies one, and they show how to look for electical problems. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned get a wiring diagram if possible to see what all is in that circuit.i assume the fuse box or booklet indicates the name for the fuse involved?things are not always what they seem.dead ends and befuddlement can originate in making wrong initial assumptions. |
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