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Parasitic Short

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Old 01-02-2006, 09:52 PM
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Default Parasitic Short

I'm so angry...

For 2 years now, ever since I bought the car, I've been trying to track down the short in my car.

I checked the draw at the battery (a few volts). I checked the draw at all the fuses, one by one, and only the radio/cluster fuse (i.e. 9C) had a voltage draw. Fuse in (.15 - .25 volts), fuse out (4.54 volts). I know the previous owner pulled out a CD radio from another bonneville and put it in this car. I replaced the blower fan and the temperature control module because my fan quit working. My blower fan was cutting in and out last winter and finally died. My temp. control module was bad, but I suspect was caused by the short. Now this winter the same thing is happening again. I can't afford to shell out another $100 bucks for another damn temp. control module. I found water in one of my tail lights and had to silicone. the other tail light is brand new. My AM doesn't work on my radio. My "low coolant" light comes on every once in a while. My LED light does not come on for my traction control, nor does it display if it is on or off on the console. My car will run really bad every once in a while, and then just work out of it. If I leave my car sit for a weak the battery will be dead. This is just a short list of the phenomenological activity that is point towards a short in my car.

If I pull the fuse that has the draw, 9C, then my blower fan won't work. If it was that easy I would have done it by now.

How can all of the above phenomenon be explained by just fuse 9C? I can't believe all those circuits are tied to 9C.

God this problem is starting to haunt my night mares. If I had a warm shop, with all the tools to work on my car, it would be better, but I have to work outside in the freezing cold with minimal tools. That sucks.

I put a off switch on my battery so my battery doesn't die after a week. But I have to physically turn it off and on every time I drive. Open the hood, close the hood, open the hood, close the hood, how monotonous.

HELP ME!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!
:?: :?: :?: :?: :?: :?: :?:
Old 01-02-2006, 10:22 PM
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You've got quite a Spring time punch list there. In order to check for a parisitic draw, you need to measure the current (amps) not the voltage. This is done in series between the source and load rather than in parallel like you would to check voltage. I think your readings are a bit obscured by your method of testing but you're on the right track. Either that or you are simply using the wrong term. The draw measured at the battery will be the sum of all of the circuits. It'* best to start there and have a helper disconnect the fuses one by one while you monitor the current draw.

What is the total current draw to start with? Can you hear your ELC compressor running often? Any devices plugged into the 12v outlets i.e. cell phone charger, MP3, other electronic gizmos?
Old 01-02-2006, 10:32 PM
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Here is a website with list of steps using a "voltmeter" not an ampmeter. I think you can use either one, but the method is different for each. I'm going to try these steps using my DC voltmeter.
http://www.carcraft.com/howto/53318/index2.html

If I'm off track let me know. These website above uses a voltmeter (?) and a test light. What is the difference between using a voltmeter and a test light? Why can't you continue to use the voltmeter for the rest of the steps?

My ELC fuse is pulled and been unplugged for some time.
Old 01-02-2006, 10:34 PM
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What is the total current draw to start with?
Honestly I never wrote down if I was measuring amps or volts. Next time I'm taking a sheet of paper so that I can write down both numbers at every step.

Can you hear your ELC compressor running often?
Fuse removed and been unplugged for some time.

Any devices plugged into the 12v outlets i.e. cell phone charger, MP3, other electronic gizmos?
No, none.
Old 01-02-2006, 10:36 PM
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I had the altenator checked last winter and it tested fine.

The altenator is only 3 years old and the battery is only 1 year old.
Old 01-02-2006, 10:49 PM
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Doug, using voltage instead of current is more of a 'rough' procedure. You're looking for a slow parasitic draw. You need to know how many amps are being drawn. Do as suggested, and report the current numbers. Have your helper in the car with the doors shut. Interior lights and all other components should be off. Make sure Retained Accessory Power is not active. While you watch the meter under the hood, your helper will pull fuses one at a time. Note which one caused how much current loss.

Being a winter-only problem (from your description) I'd be looking at a leaking windshield or climate control plenum allowing moisture into the electronics in the dash, causing a partial short.
Old 01-02-2006, 10:53 PM
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Sometimes the term "voltmeter" is used in place of "multimeter" which tests voltage, current, resistance, etc. Voltage and current are two different things and must me tested two different ways. A testlight is another method for testing voltage and a very poor tester of current.

Here'* a typical multimeter:


When testing voltage, the positive probe will be plugged in the far right hole and the negative will be plugged into the COM hole. The dial is set to the V DC area and the probes are attached in parallel (one to positive and one to negative). When testing current, the positive probe is plugged into the far left hole (see A for Amps) and the negative is still in the COM hole. The dial is set to the A scale (the fuzzy red part in the pic). You need to disconnect the positive battery cable and connect the multimeter leads in series which means that the red lead touches the positive battery terminal and the black lead touches the positive battery cable.

This will enable you to accurately find what circuit is at fault.
Old 01-02-2006, 11:14 PM
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http://www.carcraft.com/howto/53318/index.html
http://www.carcraft.com/howto/53318/index2.html

Why can't I use the steps from the internet site to find my short? The site says that the instructions are for use with a voltmeter not an ammeter.
Old 01-02-2006, 11:16 PM
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What is retained accessory power?
Old 01-02-2006, 11:18 PM
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Doug, please use a multimeter set for current (amps) or an Ammeter. That'* the language and procedure that is preferred by professionals and us. Because it'* far more accurate.

RAP is why your stereo stays on when the ignition is off. It'll stay on for 2 minutes or until you open a door. Make sure the key is not in the ignition, windows already rolled down for communication. Your helper should be small enough to worm under the dash with the doors closed to pull fuses.


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