How to find an electrical drain

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==Overview==
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'''OVERVIEW'''
If your vehicle engine fails to crank over and start after sitting overnight or longer but will start and run when "jumped", you may be experiencing a parasitic draw -- an excessive power drain when the vehicle is turned off and not in use.
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The test procedures below will help you to find the component(s) responsible if you are experiencing a parasitic draw. Parasitic draws occur when a component of your vehicle continues to use power from your battery when the vehicle is not in use. The most common causes are user-controlled devices. Although anything that uses power can potentially go bad and cause a draw. Some of the more common items are: phone chargers left plugged into a power point, lights (interior or exterior) left turned on, lighted vanity mirrors, cigarette lighters, glove compartment light, and aftermarket accessories (radio amps, CB's, etc.) left powered on.
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If your vehicle engine fails to crank over and start after sitting overnight or longer but will start and run when "jumped" you may be experiencing a parasitic draw. (an excessive power drain when the vehicle is turned off and not in use.)
 +
The test procedures below will help you to find the component(s) responsible if you are experiencing a parasitic draw. (electrical drain)
 +
Parasitic draws occur when a component of your vehicle continues to use power from your battery when the vehicle is not in use. The most common causes are user controlled devices. Although anything that uses power can potentially go bad and cause a draw, some of the more common items are, phone chargers left plugged into a power point, lights (interior or exterior)left turned on, lighted vanity mirrors, cigarette lighters, glove compartment light, and aftermarket accessories (radio amps,CB's) left powered on.
  
  
===Acceptable amperage draw===
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'''ACCEPTABLE AMPERAGE DRAW'''
Exact maximum allowable draw is determined by calculating several factors. But, as a general rule, the maximum should not exceed 50mA or .050 Amps.
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==Tools and equipment==
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Exact maximum allowable draw is determined by calculating several factors. But, as a general rule,the maximum should not exceed 50mA or .050 Amps'''
#Battery tester/charger
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#Digital volt ohm meter (DVOM), set to the DC "Amp" setting.
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#12-volt test light.
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#Proper hand tools to disconnect the negative battery cable.
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#Suitable fuse puller (a small pair of needle nose pliers work well).
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#Wiring diagram of related circuits. (May need to obtain at a later time).
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==Preliminary inspection==
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# '''TOOLS AND EQUIPMENT'''
#Test your battery and verify that it is capable of holding and has a full charge.
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## Battery Tester/Charger
#Using the test light, check all fuses and replace any that are blown.
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## Digital Volt Ohm Meter (DVOM) SET TO THE DC"AMP" SETTING
#Do a visual inspection of common problems: missing or loose ground wires, aftermarket radio or lights on a circuit always powered ON and not a switched circuit.
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## 12 volt test light
#On older vehicles, you can get in the vehicle with all doors closed and not worry about a timeout interval. Perform an under dash visual inspection.
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## Proper hand tools to disconnect the negative battery cable
#On most late model vehicles equipped with a Vehicle Control Module (VCM)and/or Body Control Module (BCM) there may be a timeout interval. A certain amount of time has to pass in order for the VCM and/or BCM to enter sleep mode where the computers will use less power. These are vehicle-specific, and you will need to consult a proper service manual.
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## Suitable fuse puller (a small pair of needle nose pliers work well)
#It is suggested that you consult the owners manual, if possible, in order to familiarize yourself with the location of all fuse boxes. You will also need to verify that you have a legend for the fuses telling you what amp fuse to use in each circuit and what components the fuse feeds power to. At this time you will also need to determine which fuse feeds power to the interior lights: often it is labeled "courtesy".
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## Wiring diagram of related circuits. (May need to obtain at a later time)
 
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# '''PRELIMINARY INSPECTION'''
==Testing==
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## Test your battery and verify that it is capable of holding and has a full charge.
 +
## Using the test light, check all fuses and replace any that are blown.
 +
## Do a visual inspection of common problems. (missing or loose ground wires, aftermarket radio or lights on a circuit always powered ON and not a switched circuit)
 +
### On older vehicles you can get in the vehicle with all doors closed and not worry about a time out interval. Perform an under dash visual inspection.
 +
### On most late model vehicles equipped with a Vehicle Control Module (VCM)and/or Body Control Module (BCM) there may be a time out interval.(A certain amount of time has to pass in order for the VCM and/or BCM to enter sleep mode where the computers will use less power.These are vehicle specific and you will need to consult a proper service manual.)
 +
## It is suggested that you consult the owners manual, if possible, in order to familiarize yourself with the location of all fuse boxes. You will also need to verify that you have a legend for the fuses telling you what amp fuse to use in each circuit and what components the fuse feeds power to. At this time you will also need to determine which fuse feeds power to the interior lights: often it is labeled "courtesy".
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# '''TESTING'''
 
## Ignition key off and all doors closed, and, ALL aftermarket accessories turned OFF. If the vehicle is equipped with an under hood light you will need to disconnect the wires going to it or remove the bulb.  
 
## Ignition key off and all doors closed, and, ALL aftermarket accessories turned OFF. If the vehicle is equipped with an under hood light you will need to disconnect the wires going to it or remove the bulb.  
 
## Disconnect the negative battery cable.  
 
## Disconnect the negative battery cable.  

Revision as of 20:27, 17 October 2009

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