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Dying battery

  • Thread starter Thread starter timboski
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timboski

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1981 vette after sitting a few day's battery is completely dead,so I purchased a new one and it is now drained after 3 day's.I did recently Have a new a/c compresser installed and the system recharged.,is there any chance the compresser is draing the battery ..

Any other idea's???to what could cause the drain.No problem's till the a/c was worked on...
 
This taken fron a post by 81Red in 2002.....thanks go to him.


Here are the steps I followed to diagnose and track the current draining culprit in my electrical system. Hopefully this can be a help to those of you who have similar problems.

Tracking electrical problems can be hit-or-miss, so begin the process by setting a plan and order of what you will be checking. Unless you are very suspicious of one or two areas that you think are most likely, start with the fuseblock circuits, and then move to the alternator and starter circuit.

TOOLS: You will need a multimeter with a 10 amp rating, preferably digital. To assist you in checking the fuse block circuits, you will want to make a simple fixture. Take a burnt-out fuse (or take a new fuse and poke out the fusible link) and file away some of the plastic on the top of each metal leg, and solder a 12-inch length of wire to each leg. Now attach an alligator clip to the end of each wire.

PROCEDURE: Remove the negative battery cable from the battery. Take the multimeter and set it to the highest current reading level (10 amp setting). Attach one meter lead to the battery cable and one to the battery. Any circuit in the car that is active will draw current and will be reflected with a reading of some value. This value of amperage will directly draw down the battery. Write down the value.

The acceptable value for parasitic current drain, as listed in the GM service manual, is approximately 35 milliamp (.035 amp). If the reading you recorded is 35 ma or less, your electrical system is behaving normally. If the value is greater, there is a current drain present that will draw the battery charge down. In my case, I read 350 ma (.35 amp) and this current drain discharged a new battery in five days. This is equivalent to a 5-watt light being on all the time.

Proceed to the next step.

FUSEBLOCK: Reattach the battery cable. Move your driver seat back, get on your knees with a flashlight, and locate the fuseblock under the dash on the left side of the firewall. Start in a convenient corner and take one fuse out. Replace the fuse with the new pigtail fuse fixture. Clamp the ammeter onto the two leads. Record your reading. If the reading is zero, your circuit is "open" and therefore not drawing current. This is good. Replace the fuse and move through the entire fuseblock to check each circuit. Write down the readings. NOTE: Do not attempt to energize any circuit while performing this test. You are measuring drain current only. The meter is not intended to pass the large current load required to run equipment or lights!

From the twelve or fifteen fuses you may have, you will have a list of milliamp readings, most of them zero. Add them up and see if they total over 35 ma. I can report the ECM computer module draws about 5 ma, and my courtesy light circuit was pulling around 30 or 32 ma. With everything added up, I had not yet identified the problem.

Proceed with the next step.

ALTERNATOR / STARTER: Disconnect the negative battery cable and attach the meter leads. You should again be reading the current drain amount. Open the hood. Find the 6-pin harness connection located next to the firewall by the heater fan enclosure. Disconnect it. Check your meter reading. If it drops to near zero (as mine did), you have isolated the drain to the starter or alternator circuit.

Start with the alternator - disconnect the heavy red wire from the back of the alternator (10-mm nut). Check your meter. If no change, then disconnect the two-wire harness from underneath the alternator. This ties into the voltage regulator circuitry. When I pulled mine off, the meter dropped to near zero. Problem found!! I chose to replace the entire alternator since mine was already a rebuilt Delco. With the new one in hand, I performed a quick check by grounding the new alternator with alligator clips and attaching the two-wire harness. The meter still showed near zero current. Problem found and verified!

If the alternator checks out okay, head for the starter circuit, or a garage lift, since access is very limited. Disconnecting the solenoid wire should give you the answer you need. I received advice from one club member who reported that new starter installations could result in current drain if the wires get placed too close to the exhaust manifold to allow the insulation to melt.

SUMMARY Locating electrical problems can be very frustrating and particularly unrewarding when you think you’ve solved your problem, only to find a dead battery days later when you least expect it. After you're through getting "advice from everybody", make a plan and begin your systematic search for the current drain(s). Get or borrow a digital multimeter, separate the negative battery cable from the battery, and measure the current drain. This is your target: to find the circuit or circuits that are responsible for this current drain. When you understand what is happening at the battery, you will know what you are looking for, and will not be tempted to stop at the first leakage point you discover.
 
This is a simplier method. Buy a 12 volt test light if one is not availaible. Disconnect the neg. battery cable, attach the alligator clip of the test light to the battery cable and the stick part of test light to neg. battery post. Make sure all accessories are off, door closed ect. If the test light lites up there is a battery drain from an accessory somewhere. Pull each fuse one at a time until light go out, and that will be your culprit.
 

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