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electrical question/advice

spyysee

Well-known member
Joined
Jun 15, 2002
Messages
124
Location
NY LI Metro
Corvette
1987 black beauty, all ez mods, owned '62,'78
battery/electrcal drain

OK..
I've replaced the battery,alternator, starter motor; all within the past 6 months.
Why?
2 reasons. one, excessive battery drain. two, 128000 mi and
15 years.
As the original owner ,i've always, since day one, felt the drain on the battery
very excessive over the course of ownership. (5 batteries and 3 alternators later)
but it has gotten much much more severe in the past month since
I've started to drive it regularly.
I bought a 1 amp trickle charger and kept it on every night.
But after a full day of being idle, the starter barely cranks.
the voltage is down to 10.5 before I cranked it.
Had the battery load tested, had the alt checked..OK
I disconnected the battery overnight and re-connected in the
morning..started fine.
I took a 12v brake light, disconnected the neg cable,placed the bulb in series with the battery terminal, and it lit at full brightness.
The charging volts reads 13.5-14volts when running.
What is wrong here???
 
D

DkBG

Guest
This is one for the experts . They'll probably see your post tommorrow . Sounds like a major short to me . Totally draining batteries does seem to kill their life . Cliff
 
R

RalleyRed

Guest
It is going to take someone that knows more about vehicle electrical systems than me to help you.

But I do agree it's a short somewhere.

I've had the same type of problem since putting my car together, I take my battery cable off nightly, I've never put a charger to my car and just replaced the battery this year after 12 years.
I'll look for and fix my short where I redo the interior.

If you've got a meter you can take a reading between the battery post and the wire, then remove fuses til you find out which system is drawing the power after that your in for the fun of figuring out what part of that system is messed up.

Goodluck,

Rick
 

cntrhub

Well-known member
Joined
Jun 17, 2002
Messages
390
Location
North Hollywood, Ca.
Corvette
Miss my '62 & '80 4- Sp. Vettes
I think the standard current draw from the battery's negitive post to the ground cable is, 1.4 ohms? If I am not mistaken, this is just enough current to keep the clock, alarm, and ECM running with the key turned off.
Anyway, it sounds like you have what's known as a, "parasitic draw." There is something draining off the battery in high voltage. The attack for this problem, is to start pulling individual fuses until you don't see an arc at the battery post and cable. Of course, use good judgment when touching the battery cable back to it's post. You will have less of chance of damage, (an explosion) if you work with a cold battery. This way, the gas bubbles are not escaping and cause an explosion. Use protective glasses working near this acid bomb.
You can take two approaches to isolate the draw from the battery. Pull the fuses one at a time, then check the cable arc at the battery post. Or, a more safe approach, is to keep the battery cable on, and pull all the fuses....then, take each fuse and begin reinstalling them back into their holder's fuse block. Put one fuse end in first, and then watch the arc as you make contact to the other side. You want to just touch the other side's U holder. If this fuse end sparks quite bright and blue, you've found the short in that circuit branch. You will need a wiring circuit diagram from the shop manual, and trace all leads to trouble source.
Parasitic draws are usually current to ground. So, some wire somewhere is bare, and either touching to ground, or is squeezed to ground. Squeezed meaning that... some component was removed and when replaced, a clump of wires behind the reinstalled component, is now (one wire usually) squeezed out of it's sheathing and is grounding. If you see just a slight spark, this my just be either of the components stated above. You will know the difference right off between needed current spark, and parasitic arc! Always test with key off, and don't be in fear of shock...you are working with DC current.
Did you, or the previous owner add an aftermarket part to the car? Was there something done to the car that a component was removed and replaced in the past? I would think back to previous work done to chase what sounds like a wire short.
 

jeepie

Well-known member
Joined
Feb 6, 2002
Messages
162
Location
Dunmore, Pa.
Corvette
1991 Coupe Blk/Blk
You can try disconnecting your under hood lights first, just follow the wires and find the plug on each side, they are down by the corners of the front. The other easy thing to try is check both battery cables they can get corroded inside the plastic coverings, make sure they are good if not replace them. If these things don't help I posted a way to start checking see below:

Let us know how you are making out, good luck.


The first thing I would try is unplug both your under hood lights and see if that helps.
If not I would get a screw type disconnect switch and install it on the negative battery
term. The switch will cause your radio presets and clock to be reset, but it will also give
you a perfect setup to hookup your amp meter. Once your switch is installed you can
read how much current your car is drawing just sitting, I believe if is more than 50ma
you have a problem (there should be no draw since your hood lights are unplugged
and all doors are closed).
In order to kill your battery in a couple days I would guess you are drawing a lot more
than that. If that is the case I would remove the battery and remove all the wires from
your jump start block, which is located behind the battery, and check the draw again
with all the wires removed. This pretty much removes everything except the starter, if
you are below 50ma start
testing each wire one at a time untill you find the wire that is over 50ma, then you will
have to find what circuit it is and what is connected to it in the manual.
You can leave the battery out and use jumper cables to hook it up while testing.
Good luck.
 
L

LarryBible

Guest
Your description strongly indicates a short circuit of some sort draining the battery.

What you need to do is put an ammeter in series with one of the battery terminals. I expect that you will see one or two amp current draw, or maybe more according to your description.

While the ammeter is in series, remove fuses one by one until you see a significant drop in the current draw. When you find the fuse that does this, you've found the troubled circuit. At that point you need to do a thorough visual inspection of everything involved with that circuit.

There is a good possibility that there is a short that is not in a fused circuit. The possibility is strong because most of the fused circuits are disconnected when the key is turned off. If this is the case you will need to isolate your search in the battery cables, and other areas that are not disconnected by the ignition switch.

A factory manual or other good electrical schematic will be invaluable while chasing this down.

Good luck,
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
If you have an aftermarket alarm or aftermarket stereo, these are prime places to start looking...
[RICHR]
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Do the AMPMETER approach

It's the only way you can quantify the amount of current being drawn, so you may identify what circuts are doing exactly what as far as drain goes.

Vig!
 

spyysee

Well-known member
Joined
Jun 15, 2002
Messages
124
Location
NY LI Metro
Corvette
1987 black beauty, all ez mods, owned '62,'78
Checked all the usual suspects, lamps, cig lighter, etc.
What about the vats or courtesy lights circuitry?
 
L

LarryBible

Guest
spyysee,

Did you check with the ammeter connected. When looking for a main power supply short (which is what you are looking for) on any electronic gear, the procedure is to monitor current if the current draw is low enough that it is not a "crowbar" short, while methodically disconnecting EVERYTHING.

The easiest way for you to disconnect eveything is to start pulling all the fuses. If you remove ALL the fuses and you still have the drain, then start disconnecting everything that has a connector until the current draw takes a significant drop.

I have used this procedure on everything from Oscilloscopes to 47KV power supplies on a radar system. It works.

Best of luck,
 

jeepie

Well-known member
Joined
Feb 6, 2002
Messages
162
Location
Dunmore, Pa.
Corvette
1991 Coupe Blk/Blk
There could be a bunch of things causing your drain. Unplug the under hood lights the switches can go bad and the lights can come on when the hood is closed. Then do the amp meter and check the total draw. If high then do the jump block thing, there are several circuits that do not go through the fuse box, they are protected by fusable links. Disconnecting all wires from the jump start block should allow you to find the problem wire, then you will have to find what circuit it is and check each thing on it. You could also have bad grounds which would cause a high draw also and the wiring might be fine. The amp meter and jump start block method should find this too.
Good luck.

Al
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Just a wild thought here

I had a similar problem on my Bronco...

But the issue was the truck would sit for LONG periods of time.. and the batt would be dead!

So being cheap... I pulled the DEEP CYCLE battery out of my boat, gave her a topper charge..plopped it into my Bronco and now she sits for WEEKS and fires right up!


Maybe if you have a current drain..... this MIGHT be an answer!

Vig!
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
KEY Words: more severe in the past month

The '87 alternator has a reputation of having a short life. Most rebuilds are crappy, incomplete jobs, too.

Once a battery goes to full discharge, expect that it's life is 30% gone; NOW. Repeated cycles, such, will seriously shorten battery life.

All new cars drain a lot more power than the old ones, due to the electronics.

A deep cycle battery is not meant for an automotive application and I'd not expect normal life from it. They are meant to be much more fully discharged than an auto discharges them. Ideally, they are chargfed with a deep cycle battery charger, too.

The fuse pulling method is the proper approach, using an ammeter ( few folks have one of sufficient capacity). All else is 'shotgunning' and time wasting, unless you KNOW which component is draining it.

May we assume that your cables are not corroded and the connections are tight and clean? This includes the starter and frame round connections.

:w
 

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