<VV> Re: EM still has electrical problems

[Larry Forman]

At 09:02 PM 5/21/2005 -0400, penneyracer1 wrote:
>Hi all once again.
>           My '64 monza keeps draining batteries. I put in a new one and 8 
> hours later it was totally dead. I am asuming it has a short somewhere, 
> but I have no idea how to troubleshoot it. Today I tried a diferent 
> generator,regulator, and then the gen light came on very dim, then 
> continued to get brighter. After a ten minute drive, I shut the car off 
> and wouldn't start again. The multimeter showed varying voltage anywhere 
> from 12.60 to 13 volts. Any ideas?

Hi,
OK, since you have a multimeter you have most of what you need.  Go to 
Radio Shack and get a 1 Ohm 10 watt (or higher wattage) resistor.  Now you 
have everything you need to trouble shoot this issue.  Yes, you likely are 
having something drain the battery and it could be something as simple as 
the glove box light being on all the time or something in the generator or 
regulator shorted.  Shorts cause currents to flow when they should 
not.  One approach is to monitor these currents and eliminate alternative 
paths until you find the one where the shorted current is flowing.  Remove 
either the connection to the negative or positive terminal to the battery 
and connect the 1 ohm 10 watt resistor to the removed terminal with one 
lead of the resistor and to the battery terminal you removed the terminal 
from connect the other end of the resistor.  Now if you connect the 
multimeter across the resistor's wires on each side of the resistor you can 
monitor current flow by measuring the voltage across the resistor.  If you 
have one amp of current you will see  one volt across the resistor.  Two 
volts equals two amps of current drain.  You should see nothing if 
everything is turned off and the door lights are off and nothing is 
draining the battery.  Now disconnect some of the wires that are connected 
to the battery's positive terminal.  You could first disconnect the 
generator and see if the voltage across the resistor goes down, or the 
regulator wiring.  Disconnect the connector in the harness leaving the 
front of the engine compartment.  Continue eliminating sources of potential 
current drain, like fuses, until suddenly the voltage across the resistor 
drops to zero.  If the connector in the engine compartment causes the 
current to go to zero, reconnect it and go to the inside fuses.  You could 
also have a short in the wiring under the floor.  Once you can identify 
current flow and eliminate alternatives you are on the right track and 
slowly narrowing it down.

Some cautions are in order.  First, you cannot start the car or turn on the 
headlights with this arrangement, since you will draw too much current and 
thus too much across the resistor.  You must remove the resistor and 
restore the connection before attempting to use the car.  You must hold the 
door light switches closed or that will drain the battery.  Remember to 
reconnect everything when you are done.

HTH,

Larry