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post #1 of (permalink) Old 12-26-2001, 03:24 PM Thread Starter
 
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jeep electrical question?

Ok, today I was check all the things that the ignition switch feeds; the coil positive, the modual, the alternator resistor wire and i found something strange.With the ignition switch off I went from each wire to the battery ground and got nothing like i should have. but If I take the ground cable off the battery and meter it directly to the ground post I get battery voltage at everything I check. I even get 12 volts at the coil negative which makes absolutly no sense to me. What gives, why would I get voltage at everything only if the battery cable is disconected?

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post #2 of (permalink) Old 12-26-2001, 03:58 PM
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Re: jeep electrical question?

I'm by no means an electrical anything, in fact I have a questions I'm going to ask when the Jeep is mobile again. I would suspect though, that when you take the ground off of your battery (ground cable), that you are simply creating the natural circuit of the battery and would get battery voltage on anything you touched. Basically, I think you could get your meter to read battery voltage if you touched the frame or any point that would create the ground for the battery.

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post #3 of (permalink) Old 12-26-2001, 08:32 PM
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Re: jeep electrical question?

Strange readings happen due to the very high resistance of the meter. Never trust a reading in a circuit that has a lot of ways to ground. If there is a high resistance in the line, it is nothing to the resistance of the meter. Thus most of the voltage is dropped across the meter. If you can not tell the current that is flowing, then the reading may or may not be correct.

Basicaly if the only path to ground is thru the meter, the reading may be not what you are trying to check.



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post #4 of (permalink) Old 12-26-2001, 09:37 PM
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Re: jeep electrical question?

Sometimes, the best test equipment for the job is a test light. If you are working on a simple DC circuit, you can clip one end to the B+ , and check grounds. The module controlls the coil ground.

Using a dvom with a very high impedance voltmeter, you will read potential across any high resistance. Including your body. Hold the lead in one hand, and touch the B+ terminal with your other hand, presto, full battery voltage.

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post #5 of (permalink) Old 12-26-2001, 10:21 PM
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Re: jeep electrical question?

here's a line of bull but when you disconnectted the ground you also might have disconneccted a few things that do stay powered all the time like a radio memory, computer,clock and stuff like that. so what happens is you still have that voltage seeking a ground so with out the current flow you are almost reading battery volatage. it would be like taking a row of resistor(series) and put one side to 12v. now measure the voltage on the otherside of the resistor chain and you will read 12v(almost)(no current flow)check in between the resistors and you'll get almost the same reading now touch the other end to ground and check everything again and you'll get a whole bunch of different readings(current flow). thats if i remember what i was taught right. i heard somewhere that you only use 20% of your brain so i figured i'd party on the other 80%, well i think i burned up 90% and started on the good end first

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