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Battery Draining In Garage

8

81Red

Guest
Changed the battery out three weeks ago because it drained down two nights in a row. With a new Gold Die-Hard battery, no apparent problems until today when again it wouldn't start, after a five day rest. When running, the voltmeter is showing 14+ volts. Looks like the alternator was replaced not too long ago.

I obviously must have some current draining in one of the circuits. I guess the procedure is to put a current meter on the main power line (car not running) to establish that current is indeed flowing, then pull fuses, one by one, to find the live circuit.

Are there some obvious things I should be looking for?
Any help would be appreciated.

Bernie
 

Yoda

Well-known member
Administrator
Joined
Oct 12, 2000
Messages
4,884
Location
Amarillo, TX
Corvette
1981 UL5
Bernie,
It sounds like you have a pretty good handle on trouble-shooting the current drain.

Be sure all the light switches work, including the under hood one. Have you added or removed anything electrical? If so that would be a prime place to start the search.

You can unplug the alternator, see what happens after sitting a couple of days on a full charge, also check all around the car after dark to see if there are any lights that at still lit.. may it be every so dim.

Good Luck,, remember to check grounds ;)
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Same here

Bernie,

I can also tell you that the same thing happened to me as it did to Grizz. The vanity mirror plunger-type switch was stuck in the on position. This will happen with the mirror cover down or lowered. The light is not always easy to see.
 
8

81Red

Guest
Battery Draining Problem

Problem solved!!!

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.

Have patience, and happy hunting.



Bernie
 

Yoda

Well-known member
Administrator
Joined
Oct 12, 2000
Messages
4,884
Location
Amarillo, TX
Corvette
1981 UL5
Bernie,

That is one of the BEST descriptions on Electrical Trouble-Shooting I've seen.. Excellent write up...

I copied it to word, with your permission and credits I would like to incorporate this into the L81VetteRegistry Tech pages..

BudD
:bu :w
 
8

81Red

Guest
Bud,

permission granted.

And big thanks to all those who have offered help along the way.

:BOW

Bernie :)
 

Nut

Well-known member
Joined
Oct 15, 2000
Messages
890
Location
Bowie, MD
Corvette
Vette-less for now
Bernie.... I couldn't agree more with Bud. It's already tacked on my garage wall for a quick reference. I got EE's working for me that couldn't have described that analysis in such excellent detail. Want a job back east? :D

Thanks............ Nut
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
wow

81Red,

That is some piece of work...I guess patience pays big dividends.
;)
 

herron

Well-known member
Joined
Jul 19, 2006
Messages
98
Location
Michigan
Corvette
1981 T-Top, Silver over Blue
Anyone know where to find one of those vanity mirror plunger-type switches for an '81?
 

mdazzo

Member
Joined
Mar 26, 2005
Messages
24
Location
mastic,new york
Corvette
1979 #19-black
Problem solved!!!

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.

Have patience, and happy hunting.



Bernie
ALTERNATOR / STARTER: Disconnect the negative battery cable and attach the meter leads.

bernie what leads am i connecting to ?do you mean in between the negative cable and the negative battery post?
thanks matt
 

Yoda

Well-known member
Administrator
Joined
Oct 12, 2000
Messages
4,884
Location
Amarillo, TX
Corvette
1981 UL5
:w Matt,

The amp meter needs to be placed in the circuit in Series ;) or one lead of the meter (-) goes to the output of the alternator and the other amp meter lead (+) goes to the lead you removed from the alternator ;)

Alternator.......(-) amp meter lead, amp meter, then the other amp meter lead to the removed lead from the Alternator

ALT... Amp Meter... Alt. Lead

Bud
 

WONKABOY

Well-known member
Joined
Oct 31, 2004
Messages
237
Location
BRIDGEPORT , CT
Problem solved!!!

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.

Have patience, and happy hunting.



Bernie

What was your problem?
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Bernie,

Your write-up was very useful...specially since I believe that my car's vanity mirror was causing the drain in my Vette's battery.

So I disconnected the vanity mirror harness and removed it. One minor obstacle though. My Vette's battery was completely drained (it only had 0.83 volts in it).

I had to re-charge the battery, and then follow-up your procedure. I plan to check again tomorrow to see if the battery was drained somewhat. I took a long drive on Saturday afternoon, and I thought I noticed my ammeter in the Vette was barely charging a positive charge, but another look today made me realized that it is charging just fine (it is to the right of the "13" center value). I also noticed that the needle does not move from RPM change, but it does move when the blinker is on.

Today I did check your procedure again, and I noticed a couple of things that gave me some doubt. First, when I place the ammeter in series as you explained in the procedure, I get "negative zero point zero zero". I get this whether the meter is in the 20 amp, 400 mamp, or 4 mamp scales. But more noticeably, the interior lights don't come-on (since I need the driver door open when following your procedure. Shouldn't placing the multimeter (in the ammeter setup) close the circuit path for the door switch to make the interior lights come on? I recognize that perhaps it has to do with the power distribution, but there lies my element of doubt. I also read that a circuit should be completed to be able to read the current draw or how fast are the volts flowing through the existing resistance?
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Lucky break

Hey!

I found what was causing my Vette's battery to drain in about 5 days.

It was the automatic antenna motor.

It was a lucky break, though. I wish I could report some savvy procedure, but there was none.

I was sitting in the Vette after charging my battery, and after the first 5 minutes, I noticed the interior lights to flicker or dim somewhat. Later I noticed that there was an almost inaudible clicking going on when the dimming took place. Following the clicking sound (for about 2 hours) led me to the rear of the Vette and then to the antenna. I felt my way around, and Bingo! The motor was warm to the touch.

Today I drove it to work, and it started right-up. I am happy! :upthumbs
 

mp3 Maker

New member
Joined
Aug 25, 2007
Messages
4
Location
Aventura, FL
Corvette
1970, 1979, 1981, 1993, 2003,
I was having the same problem it wound up being my ECM and the factory alarm
 

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