diagnosing a mystery current drain

wc701lists at bellsouth.net wc701lists at bellsouth.net
Tue Nov 18 15:30:55 CST 2008

davidpertuz at mindspring.com wrote:
> My G20 has been suffering from dead batteries recently, and while the initial investigation pointed to a bad battery, it now seems to be pointing to some unknown current draw when the car is off. The battery will go down to 3.x volts in about a day when in the car, but seems to be normal (so far - it's only been overnight) when out of the car. 

Put your multi-tester on the highest DC current setting, and hook it in 
*series* with a battery terminal.  A lot of people get his wrong...  you 
need to disconnect a battery terminal and put one probe of the tester on 
the battery, and one on the terminal.

Ok, hopefully your tester did not just go up in smoke  ;)  They usually 
have a 10A or higher setting and a fuse for just such a cause.

If it's running down in a day, you're probably now reading a fraction of 
an amp.  Now pull each fuse and look for changes in the reading.  When 
it drops way off, you've identified the circuit causing the problem.


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