[DeTomaso] Why Is My Battery Discharging?

[SOBill at aol.com]

Ed,
 
At http://www.panteraplace.com/Electrical/Power%20Distribution.pdf you  
will find a diagram showing the electrical power distribution on the  Pantera. 
This diagram is the Big Picture based on a stock Pantera electrical  system 
and was made at the suggestion of and with the help of Lee Farrell.
 
How to find out why a battery is discharging?
 
Disconnect the negative battery cable. Now the battery can not be  
discharging into any circuit in the car. Measure the battery voltage with a  
multimeter which can read to at least 0.01 volts. Such meters are readily  
available and are quite inexpensive. If your battery voltage is slowly  decreasing, 
the battery is being discharged. What does "slowly deceasing"  mean? My 
battery voltage did not vary by +/- 0.01 volts measured over 5 minutes.  If your 
battery voltage is slowly decreasing when the battery is not connected  to 
any load, you have a bad battery.
 
If the battery is good, why is it discharging?
 
Reconnect the negative battery cable to the battery. Measure the battery  
voltage. If the battery voltage is decreasing, the battery is  discharging 
thru a load in the car. Looking at the Power Distribution  Diagram. How can 
the battery discharge? The battery could discharge thru the  Alternator, the 
Ignition Switch, the Headlamp Switch, or Fuses 7,8, or 9. Since  the Headlamp 
Switch is OFF, and the Ignition Switch is OFF, the battery could  only 
discharge thru the Alternator or Fuses 7, 8, or 9. Since the fuses are  
relatively easy to get too, pull Fuse 7, If the battery voltage continues to  drop, 
replace Fuse 7 and pull Fuse 8. If the Battery voltage continues to drop,  
replace Fuse 8 and pull Fuse 9. If the battery voltage continues to drop,  
replace Fuse 9. Unless there is more than one problem, we have eliminated the  
circuits associated with Fuses 7, 8, 9 as the source of the problem. On the 
 assumption that we have a single circuit causing the problem, I recommend  
pulling and replacing fuses one at a time. It is no fun to wind up with a 
pile  of poorly marked fuses to sort out against a diagram. A more scientific 
 approach, which accommodates multiple causes for the problem, is to pull a 
fuse,  mark it as to location, and do not replace the fuse until we have  
solved the problem. Do it which ever way makes the most sense to you.
 
The next item to test would be the Alternator, but, since fuses are easy  
to access, pull fuses one at a time and recheck the battery voltage.  If you 
pull a fuse and the battery voltage stops dropping, you have found  the 
circuit that is draining the battery. If you have tested all the fuse  circuits 
and the battery voltage is still dropping, the only component left is  the 
alternator.
 
To this point, we have had life fairly easy and we should be done is less  
than one hour. Life, unfortunately, is going to get a little less easy. We 
must  get to the Alternator.
 
How to find out if the drain is in the Alternator?
 
Disconnect the negative battery cable from the battery. At the rear of the  
Alternator remove the Big Black wire and be sure it does not touch the 
chassis.  Reconnect the battery negative cable to the battery. If the battery  
voltage continues to drop, the problem is not in the alternator. If the  
battery voltage stops dropping, the diode pack in the alternator is the most  
likely problem. Any auto electric shop can easily fix this problem.  
Disconnect the negative battery cable. Reconnect the big black wire at the  
alternator. Reconnect the battery negative cable to the battery.
 
If you have done all of these tests and the battery voltage still continues 
 to drop, something quite strange is happening IF YOUR CAR IS STOCK. If 
your is  not stock, disconnect whatever is not stock and see what happens.
 
This all sounds quite complicated, but it really is not. Look at the  
diagram, think of what you eliminate when you pull a fuse. There is no magic: No  
Fuse = No Drain. The problem can be found.  Let me know what you find in  
any case.
 
SOBill
 
The main  thing is to keep the main thing the main thing.
Do the best you can with what  your have where you are.
Have fun today!
SOBill  



-------------- next part --------------

   Ed,

   At
   [1]http://www.panteraplace.com/Electrical/Power%20Distribution.pdf you
   will find a diagram showing the electrical power distribution on the
   Pantera. This diagram is the Big Picture based on a stock Pantera
   electrical system and was made at the suggestion of and with the help
   of Lee Farrell.

   How to find out why a battery is discharging?

   Disconnect the negative battery cable. Now the battery can not be
   discharging into any circuit in the car. Measure the battery voltage
   with a multimeter which can read to at least 0.01 volts. Such meters
   are readily available and are quite inexpensive. If your
   battery voltage is slowly decreasing, the battery is being discharged.
   What does "slowly deceasing" mean? My battery voltage did not vary by
   +/- 0.01 volts measured over 5 minutes. If your battery voltage is
   slowly decreasing when the battery is not connected to any load, you
   have a bad battery.

   If the battery is good, why is it discharging?

   Reconnect the negative battery cable to the battery. Measure the
   battery voltage. If the battery voltage is decreasing, the battery is
   discharging thru a load in the car. Looking at the Power Distribution
   Diagram. How can the battery discharge? The battery could discharge
   thru the Alternator, the Ignition Switch, the Headlamp Switch, or Fuses
   7,8, or 9. Since the Headlamp Switch is OFF, and the Ignition Switch is
   OFF, the battery could only discharge thru the Alternator or Fuses 7,
   8, or 9. Since the fuses are relatively easy to get too, pull Fuse 7,
   If the battery voltage continues to drop, replace Fuse 7 and pull Fuse
   8. If the Battery voltage continues to drop, replace Fuse 8 and pull
   Fuse 9. If the battery voltage continues to drop, replace Fuse 9.
   Unless there is more than one problem, we have eliminated the circuits
   associated with Fuses 7, 8, 9 as the source of the problem. On the
   assumption that we have a single circuit causing the problem, I
   recommend pulling and replacing fuses one at a time. It is no fun to
   wind up with a pile of poorly marked fuses to sort out against a
   diagram. A more scientific approach, which accommodates multiple causes
   for the problem, is to pull a fuse, mark it as to location, and do not
   replace the fuse until we have solved the problem. Do it which ever way
   makes the most sense to you.

   The next item to test would be the Alternator, but, since fuses are
   easy to access, pull fuses one at a time and recheck the battery
   voltage. If you pull a fuse and the battery voltage stops dropping, you
   have found the circuit that is draining the battery. If you have tested
   all the fuse circuits and the battery voltage is still dropping, the
   only component left is the alternator.

   To this point, we have had life fairly easy and we should be done is
   less than one hour. Life, unfortunately, is going to get a little less
   easy. We must get to the Alternator.

   How to find out if the drain is in the Alternator?

   Disconnect the negative battery cable from the battery. At the rear of
   the Alternator remove the Big Black wire and be sure it does not touch
   the chassis. Reconnect the battery negative cable to the battery. If
   the battery voltage continues to drop, the problem is not in the
   alternator. If the battery voltage stops dropping, the diode pack in
   the alternator is the most likely problem. Any auto electric shop can
   easily fix this problem. Disconnect the negative battery cable.
   Reconnect the big black wire at the alternator. Reconnect the battery
   negative cable to the battery.

   If you have done all of these tests and the battery voltage still
   continues to drop, something quite strange is happening IF YOUR CAR IS
   STOCK. If your is not stock, disconnect whatever is not stock and see
   what happens.

   This all sounds quite complicated, but it really is not. Look at the
   diagram, think of what you eliminate when you pull a fuse. There is no
   magic: No Fuse = No Drain. The problem can be found.  Let me know what
   you find in any case.

   SOBill

   The main thing is to keep the main thing the main thing.
   Do the best you can with what your have where you are.
   Have fun today!
   SOBill

References

   1. http://www.panteraplace.com/Electrical/Power%20Distribution.pdf