me with my battery again..........
11-05-2001, 01:42 PM
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me with my battery again..........
<center><img src="http://pictureposter.audiworld.com/26260/ammetertest.jpg"></center><p>Ok, ive posted a few times on trying to find a ground that is running my battery down in my 90S. I got the proper ammeter to test the amps that are being used, however im rather incompetant when it comes to these types of things, i was told that my car was positivly grounded (??? maybe not, didnt make much sense to me excpet for the extra red wire on the positive terminal) anyways i have been trying to test my car as shown in the poorly drawn diagram above. The only thing is, when i hook it up like that, the needle jumps, then goes back down, then doesnt work at all, i geuss shorting the thing out. Ive already gone through 2 of the ammeters and im gonn alook really dumb goign back to Radio Shack every 2 days to replace something i broke. So my question is, how do i go about properly testing the amperage?
11-05-2001, 03:01 PM
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Re: me with my battery again..........
Hi.
I wouldnt think that your car was positively grounded as this is quite rare. All the 'grounded' part means is that the battery terminal (pos or neg) is attached directly to the body of the car via a thick wire, and the systems in the car use the body as the ground/return 'path' to the battery.
The fact that you have blown 2 ammeters connecting them as shown shows pretty conclusively that there is a major short somewhere, drawing tons of current, but I am surprised that none of your fuses have blown out if that is the case.
I would look for chafed wires etc on some of the more major circuits of the car. For instance in some (all?) cars the starter motor & solenoid is directly connected to the battery + via a chunky cable, things like that that could cause an open circuit at the battery if chafed.
Also, if the battery is old (3yrs+) they can tend to short themselves out as the plates inside warp and can touch each other. No amount of charging will cure this. Have you had the battery tested?
HTH
Graham
I wouldnt think that your car was positively grounded as this is quite rare. All the 'grounded' part means is that the battery terminal (pos or neg) is attached directly to the body of the car via a thick wire, and the systems in the car use the body as the ground/return 'path' to the battery.
The fact that you have blown 2 ammeters connecting them as shown shows pretty conclusively that there is a major short somewhere, drawing tons of current, but I am surprised that none of your fuses have blown out if that is the case.
I would look for chafed wires etc on some of the more major circuits of the car. For instance in some (all?) cars the starter motor & solenoid is directly connected to the battery + via a chunky cable, things like that that could cause an open circuit at the battery if chafed.
Also, if the battery is old (3yrs+) they can tend to short themselves out as the plates inside warp and can touch each other. No amount of charging will cure this. Have you had the battery tested?
HTH
Graham
11-05-2001, 07:42 PM
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Hook up is OK, he is probably blowing a fuse inside the ammeter.
It doesn't matter which terminal. If the polarity is right (looks good to me, and his needle is "jumping up" the right way.
11-05-2001, 08:09 PM
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What is the range on that ammeter Ben? 2amps DC is the absolute minimum.
If I recall the car will draw abbout 10? 15? milliamps to keep the radio memory, etc.
You need to get the ammeter working OK and the start pulling fuses until you find the prolem.
Last time I did this was on a 1988 80. It had a mis-adjusted trunk light switch that never turned off.
Seems like Shucks has some decent digital multimeters for $50..
You need to get the ammeter working OK and the start pulling fuses until you find the prolem.
Last time I did this was on a 1988 80. It had a mis-adjusted trunk light switch that never turned off.
Seems like Shucks has some decent digital multimeters for $50..
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11-06-2001, 04:39 PM
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making progress but...........
ok, i got a new multimeter and got it tow work as shown in my previous diagram. It has 3 range settings, 4 milliamps, 400 milliamps and 20 amps. My physics teacher suggested that my other ammeters were breaking was becasue the current was to high, so i used it on the 20 amp setting, and with everything off it reads about 3.8 amps, which explains why my battery drains in about 7 hours, however, when i put it to the 400 mA or even the 4 mA, it just reads .01. is this just because its to much amperage for that particular setting to handle? its got me all confused.
11-06-2001, 10:55 PM
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You probably blew the fuse again. The 20 amp scale will be OK but be forewarned...
the 20 amp scale probably IS NOT FUSED. You blow that out, say by turning on a bunch of lights or starting the car, the voltmeter will be broken and probably not worth fixing. You probably need to switch the hot/positive/red lead to use the lower current scales too. BUT DON"T DO THAT if you are reading 4 amps on the 20 amp scale. You will blow the fuse inside the meter again.
Since you are in Physics I assume you are measuring DC current.
If you are in doubt about a measurement always start with voltage, always start on the highest scale and work down. Your meter will appreciate it.
You really need a buddy now to start pulling fuses while you watch the amps to isolate the problem area. I bet you 25 cents if you pull the trunk light bulb out the drain will go away.
Since you are in Physics I assume you are measuring DC current.
If you are in doubt about a measurement always start with voltage, always start on the highest scale and work down. Your meter will appreciate it.
You really need a buddy now to start pulling fuses while you watch the amps to isolate the problem area. I bet you 25 cents if you pull the trunk light bulb out the drain will go away.
11-07-2001, 04:55 AM
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Re: Current too high...
The current you are reading (3.8A) is too high for any of the mA scales on your ammeter so will not register.
The lowest fuse used in the car is probably 5A hence none of them are blowing even though there is a drain because it is not drawing enough current. Try removing each fuse in the fuse box in turn and measure the current across the socket terminals until you find your 3.8A (or close to it) other systems in the car may draw some current even though the ignition is off (e.g. clock, alarm etc.) but nowhere near 3.8A. If you find it, it should narrow down the culprits.
Let me know what you find.
HTH
Graham
The lowest fuse used in the car is probably 5A hence none of them are blowing even though there is a drain because it is not drawing enough current. Try removing each fuse in the fuse box in turn and measure the current across the socket terminals until you find your 3.8A (or close to it) other systems in the car may draw some current even though the ignition is off (e.g. clock, alarm etc.) but nowhere near 3.8A. If you find it, it should narrow down the culprits.
Let me know what you find.
HTH
Graham