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Question Electical question/advise

I know this has been covered but I have bad luck whith the search. I have a major drain on the battery on my 87 930.
Got some advise to hook up a 12v bulb between the neg. cable and the neg. post on the battery and the light will shine with the current draw, pop fuses untill you find the circuit thats is draining the battery. I popped all the fuses one at a time and the light never went out, am I doing something wrong?
Thanks for the help
Finn

Old 03-25-2011, 04:12 PM
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Not understanding how you set up the test light. The negative cable connects to the negative post - you put a bulb between these two and it lit up?

SO the idea is that if something is drawing current it will route juice to the ground on the battery and light up the bulb? That is pretty cool if so.

If that is the test and I understand it correctly there are circuits that have no fuse that can be messing with your plan. Or there is a fuse that you are not disconnecting - like an alarm fuse under the dash.

Please keep us posted.
Old 03-25-2011, 04:27 PM
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You did disconnect the negative cable from the post. Correct?

Current Drain with ignition off
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Old 03-25-2011, 04:33 PM
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yes the neg. cable is not conected to the neg. post of the battery
Old 03-25-2011, 05:24 PM
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How old is your battery? and what do you consider "major" drain?

We lose 3-6% per day if not driven.
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Old 03-25-2011, 06:51 PM
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It is possible that you have two circuits draining current and thus the light will not go out. Did it's brightness change at all? Of course the drain could be from a connection that is not fused.
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Old 03-25-2011, 07:00 PM
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Quote:
Originally Posted by DRACO A5OG View Post
We lose 3-6% per day if not driven.
What kind of drains do you have to lose 3-6% per day?
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Old 03-25-2011, 07:12 PM
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Meter, preferably digital with an alarm....then pull fuses. Watch for an increase in voltage.
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Last edited by Joe Bob; 04-16-2011 at 01:39 PM..
Old 03-25-2011, 07:17 PM
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Unfortunately, it is the nature of our beasts.

Off hand clock will draw a bit, even dealer keep new 911's on a charger sitting in the showroom.

If your baby is a daily, no need to worry. If she is a weekend queen, then disconnecting the battery will help.
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Old 03-25-2011, 07:18 PM
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Quote:
Originally Posted by Joe Bob View Post
Meter, preferably digital with an alarm....then pull fuses. Watch for a drop in voltage.
Maybe a drop in current?
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Old 03-25-2011, 07:20 PM
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Quote:
Originally Posted by DRACO A5OG View Post
Off hand clock will draw a bit.
I have the factory analog clock. Along with the immobilizer, I am drawing 22 mA.
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Old 03-25-2011, 07:21 PM
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My bad....you will look for a RISE in voltage. The fuse being pulled will be the culprit circuit.
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Old 03-25-2011, 07:22 PM
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Quote:
Originally Posted by Traveller View Post
I have the factory analog clock. Along with the immobilizer, I am drawing 22 mA.
Yeah, very little.

Here is a test, Check voltage after a drive, then daily prior to starting her. note the decrease.
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Old 03-25-2011, 07:23 PM
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Quote:
Originally Posted by DRACO A5OG View Post
Here is a test, Check voltage after a drive, then daily prior to starting her. note the decrease.
The decrease in voltage as time goes by?

IF that is the case and IF current draw is very little, then I can come to the conclusion that battery capacity is low and it may be time for a new battery.
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Old 03-25-2011, 07:27 PM
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Yes,

No, not necessary to change the battery, it is just a characteristics of our babies.

How old is your battery?
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Old 03-25-2011, 07:29 PM
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Quote:
Originally Posted by Joe Bob View Post
My bad....you will look for a RISE in voltage.
A rise in voltage? Why, because there is no drain on the battery after removing the fuse of the circuit in question?
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Old 03-25-2011, 07:30 PM
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Go to an AutoParts store that offer free check of the battery.
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'85 Carrera Targa
Factory Marble Grey/Black * Turbo Tail * 930 Steering Wheel* Sport Seats * 17" Fuchs (r) * 3.4 * 964 Cams * 915 * LSD * Factory SS * Turbo Tie Rods * Bilsteins * Euro Pre-Muff * SW Chip on 4K DME * NGK * Sienes GSK * Targa Body Brace
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Old 03-25-2011, 07:33 PM
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Quote:
Originally Posted by DRACO A5OG View Post
No, not necessary to change the battery, it is just a characteristics of our babies.
You mean a high current drain is characteristic?

How many mA did you measure?


Quote:
Originally Posted by DRACO A5OG View Post
How old is your battery?
I put it in almost a year ago after taking possession of my 993 in September 2009.

After topping up the battery with distilled water and charging it, I was taking battery voltage measurements every few days and noticed that the voltage was decreasing far too quickly. With my 22 mA current drain, that told me I had a battery at the end of its life...a battery with very little capacity left. The date code on the battery was 2005, so it had a very short life at almost 5 years.

I performed a load test at 1/2 the CCA and it was borderline.

I'm glad I replaced it last April because a month later, my alternator belt went, 110 miles from home. The new battery with 120 minutes of RC got me home...final battery voltage was 11.4V...I charged it immediately.

The batteries in my DDs have lasted over 16 years; the one in my present car is in its 12th year. There is nothing like a low-tech flooded lead acid battery.
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Old 03-25-2011, 07:41 PM
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Yeap, replaced mine after 5 years, she would just not keep the charge.

I was lucky I changed it before it left me stranded
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Old 03-25-2011, 08:09 PM
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Battery is less than a year old, drains down from full charge to "won't start the car" 4 5 days tops

Old 03-26-2011, 06:51 AM
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