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Registered
1994 Deville
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13 Posts
Discussion Starter #1
My son has a 94 Deville that has a short in it. What we've done already is use a digital volt meter with the negative lead on the battery post and the positive lead on the battery cable. Battery charge is 12.5 volts, we get a draw between the negative post and negative cable of 12.3. We've pulled every fuse, maxi fuse and the relays under the maxi fuse with no change the the amount of volts. Is there any other relays we could try? Is it possible that the alternator or starter are shorted and is there a way to eliminate them from the circuit or test them.

We're pretty much at a standstill until we come up with something else.

Any help would be appreciated.

Thanks,
Bob
 

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Super Moderator
2010 DTS
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87,575 Posts
Can't you just pull the cable from the starter and the alternator and see if the voltage draw stops?
 

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2002 deville
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5 Posts
switch meter to amps, should draw less than .1 amps. hook up they way you are doing. give meter a couple of minutes to let everything settle down
 

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Cadillac Technician
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11,051 Posts
Yeah some confusion in the terminology here. I was confused.

You are saying the battery keeps going dead?
As stated you need to change the way you do the test and depending on the meter you need to be careful so you don't blow fuses.
The only way to measure a "draw" or "parasitic load" is to use an Ammeter.
You need to disconnect the negative cable and put one end on the battery, and one end on the cable (series).
Be sure the meter is set for at least a 10 Amp draw and hopefully it won't be more than that. Let all the modules power down and check the meter after about half an hour.
Depending on the issue it could be still hiding. The test GM has us do requires the use of a special tool, that you can actually get but....
Try this test first and post up some results.
It should be less than 50 mA.
 

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1994 Deville
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13 Posts
Discussion Starter #5
I set my DVM 20mA and put the one lead in the 10A output. It toasted the meter's fuse twice. Should I be setting the DVM to something other than 20mA? I'm assuming it's drawing quite a bit since when I hook the negative cable up to the battery it sparks a lot.

Bob
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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71,110 Posts
"Sparks a lot" is a horse of a different color - no small VOM has an internal fuse large enough to hold that current draw - most are limited to 10A, max ........In this case, hook up the battery and float it on a charger - preferably a smart charger. Now, in whatever fuse boxes you have, start pulling fuses one by one. When you find the fuse to the faulty circuit the battery charger will quickly reduce the charge rate.

IF you have a 10A setting on the VOM, start there and work down - the normal residual draw on these cars is 20 - 35 mA to start with, so you need to go higher and work down.
 

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1992 Sedan Deville, 1984 Lincoln Town Car
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759 Posts
Current (amps) = volts divided by ohms. If there is no resistance (ohms) your current draw would be +-12 DC amps. and yes there would be lots of "sparking" when you connect that wire. If it "sparks a lot" you could have a dead short to the battery. don't use the ammeter at all. Disconnect the battery- PERIOD! Think of the battery as a bomb that by shorting it out like that you could detonate it. KABOOM! With it disconnected totally from the car then use the safety first NO POWER method to check continuity. (Ohm) meter between the Positive cable and the Negative cable. Ideally, it should read infinity (1) but since you have a short it should read very low ohms. Start removing device connections until the resistance (ohms) go up and up and it does read infinity. The problem can only be something big like the starter or the alternator or even cable to cable. Maybe do the easy thing first and disconnect the alternator. If that doesn't help then climb under the car and disconnect the starter.
 
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