[DeTomaso] Why Is My Battery Discharging?
John Donahue
demongusta at me.com
Wed Dec 17 19:46:53 EST 2014
Been following this discussion, and could not resist to comment on the first sentence - 5th paragraph (I think) - since I am a veterinarian (DVM) - and have been known to be "sensitive". LOL
On Dec 14, 2014, at 5:05 PM, Larry - Ohio Time <Larry at ohiotimecorp.com> wrote:
>
>
> Hi Ed,
>
> Lots of very good advice, but I do things just a bit differently (that
> should not be surprising).
>
> I have an old "trouble light" that I have modified. Cut the 110vac end off
> and install two larger alligator type clips on the wire ends. Now change the
> light bulb to a 12 volt model. You can find them at RV stores.
>
> Now hook this between the battery post and the removed battery cable, like
> the others have said. If there is a load (drain) the 12 lamp will light up.
> Now take this light to the fuse box as others have told you to do. When the
> light goes out you found the problem. You can get good at determining the
> amp draw by how bright the lamp is after a wile.
>
> You are going to need a light anyway :)
>
> The problem with a DVM measuring voltage is that they are very sensitive. I
> have measured voltage from the positive post to the top of a dirty battery
> case.
>
> An Amp meter is the way to go but they can be costly (I have two Sun units
> for sale) and then you need to crawl out from under the dash, walk to the
> battery and bend over to read it. That takes me about 20 minutes each time.
>
> Thinks to remember:
>
> If you open a trunk, hood, door, glove box and a light normally comes on
> this will look like a drain (short) when you open them during testing.
>
> The battery is draining when the car if off and key is out, so look at the
> things that work then, horn, lights ect.
>
> You do not want to kill your new battery so do not leave it hooked up until
> you find the problem. It can also be a fire safety problem should the drain
> turn into a short.
>
> In Pantera's I have found bad horn relays, voltage regulator and I think a
> back up switch on the ZF that have done this.
>
> Larry (sparks) - Cleveland
>
>
> -----Original Message-----
> From: DeTomaso [mailto:detomaso-bounces at poca.com] On Behalf Of SOBill via
> DeTomaso
> Sent: Saturday, December 13, 2014 7:24 PM
> To: detomaso at poca.com
> Subject: [DeTomaso] Why Is My Battery Discharging?
>
>
> 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
>
>
>
>
>
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