Huge draw on battery when turned off!

[ejrempel]

My 86 Vette killed a brand new battery in 14 months. Now, it will kill a new battery in 3 days. When I hook up the neg to the battery terminal, it sparks to beat the band, and is so strong that it makes the sidepost cable stick to the battery terminal. I have: 1. pulled every fuse in the car, no luck
2. pulled the alternator wires off, no luck
3. pulled damn near every {but not every} relay apart, no luck

Is there something I am missing? Is there a certain bad relay or switch I can look to that has a history on early C4's? I gotta fix this, as it ruins the car, drivablility wise. Any help appreciated.

 

[tnovot]

I have had a similar problem that is intermittent. I also just had to get a new battery after less than 2 years. At its worst, the battery will go down in 3-4 days. Even a .75 amp battery Tender will not keep up with the discharge rate. Pulling individual fuses and testing battery draw with each pull revealed nothing. Pulling ALL fuses still did not stop the battery drawdown.
Just a few days ago, I read a recall notice that discussed battery cable(s) vibrating and/or rubbing against metal somewhere which wears through the insulation so that the battery shorts out. The car is now in storage with battery disconnected so I'll wait until spring before attempting to check the battery cables at all points on contact with metal.
Hope this helps. Good luck and please close the loop when you find the cause.
Terry

 

[billydcox]

Check the cable from the battery to the starter.

 

[MBDiagMan]

Yes, the starter cable would definitely be suspect.

You will need a high capacity ammeter since you don't know just how much current is being drawn. With all the fuses left out, connect an ammeter to the positive cable with it disconnected from the battery, then momentarily touch the other ammeter lead to the positive battery post. Note the current reading.

Now disconnect the big battery cable from the starter post and make sure it does not bend back in place and touch the post. Then touch your ammeter lead to the battery post again to make sure that the current drops to zero. If it does not then the starter cable is shorted some where. If it does drop to zero then start tracing all the other circuits that originate from the positive battery cable that are not fused, or on some cars the other hot circuits originate from the post on the starter from which you just removed the starter cable. A wiring diagram would be MOST useful for this process.

The Haynes manual is relatively cheap and has a wiring diagram that will be good enough for the purpose.

Good luck and let us know what you find or if you need more help. My wiring diagram is out in the shop. I will try to remember to get it today so that I will be better prepared to answer any specific questions, but you need a wiring diagram for yourself as well.

Best of luck,

 

[tnovot]

ej ---
Something else I should have said and wonder if your problem started the same way.
Mine started gradually a few years ago and at first the battery would take 2 -3 weks to discharge so I thought it was just from not being driven enough with anti-theft, lcd memory, etc drawing current. Also thought the older battery could be at fault so got a new battery. The problem did not show up for a while - probably because the new battery was strong enough to overcome small discharge and I used the car often enough during nice weather to keep it charged.
Then the problem got gradually worse over a 2 year period to the point like you describe. Ruined another battery so that is the history of my problem. This is when I did the testing as previously described. Anything here sound familiar?
Thanks to billy and Doc for confirmation of my suspicions that the + battery cable is at fault.
Terry

 

[vetteboy86]

Well I dont see how of the negative battery cables insulation was rubbed off and it was contacting metal would have a draw on the battery at the moment. However if the positive cable would make contact with metal or a ground you would have big problems. In fact you would probably be able to see or smell the problem, because the positive cable would get very very hot. It would ruin the battery really quick.

 

[ejrempel]

With my multimeter switched to miliamps, I was getting like 34 miliamp draw. I can't quite remember. I tell you this, the positive cable doesn't get hot, but it sure as heck sparks when you connect it. Way more than what a computer would take. It sparks as much as if I had a CD ignition hooked up, no it sparks even more than that, because my Jacobs in my Cutlass doesn't even spark like that. And yeah, I figured I just wasn't driving it enough. It has been sneaking up on me, but now, a brand new battery in 2-3 days is no problem. I wonder if I should start shooting the electrical system with an infared gun. I have a very good one. Oh yeah, I have a 2" thick GM manual with the wiring diagram. I just don't know how to read it, but a buddy of mine is an elec. wiz.

 

[MBDiagMan]

Did you have your ammeter connected in series? You need to disconnect a battery cable and put the ammeter with one lead on the cable and the other on the battery post. If you do indeed have a large current draw then you need a hefty ammeter, at least 10 Amps, preferably higher or you might blow the meter.

If you did indeed have it connected in series and only got 34 milliAmps you have nothing to worry about the problem is a bad battery or charging system, not a current drain.

Good luck,

 

[JrRifleCoach]

Check the cable from the battery to the starter.

I agree. You should also check to see if the starter and or soleniod are oil soaked. This can be another problem source.

 

[Hrtbeat1]

Auto or Manual?

I remember a TSB about the large purple wire going to the shifter (neutral saftey switch) getting rubbed and causing a short. It was routed strange under the forward part of the center console and causing some problems. The solution was to repair the cable and re route the cable where it would not get chaffed.

This is a long shot but one thing I thought of. The cable is large guage maybe 10AWG. Hope this helps.

 

[G Winter]

I remember that also. The purple wire comes from the ignition to the saftey then to the starter selenoid. The thing is that should only have current when you are attempting to crank. Is there another wire that I am not aware of ?
Glenn

 

[ejrempel]

Did you have your ammeter connected in series? You need to disconnect a battery cable and put the ammeter with one lead on the cable and the other on the battery post. If you do indeed have a large current draw then you need a hefty ammeter, at least 10 Amps, preferably higher or you might blow the meter.

If you did indeed have it connected in series and only got 34 milliAmps you have nothing to worry about the problem is a bad battery or charging system, not a current drain.

Good luck,

I did disconect the ground and put the multimeter between the battery and the cable. It was set on 10 amps. How come it sparks so much when I hook it up? I will retest this week.

 

[ejrempel]

I agree. You should also check to see if the starter and or soleniod are oil soaked. This can be another problem source.

Starter was pulled last week. Works well on the bench and is dry.

 

[G Winter]

are you sure the under the hood lights are turning off ?

Glenn

 

[oldace84]

I use a shut off switch all the time.

 

[ejrempel]

Ok, I just switched the red wire to the 10 amp setting, and then turned the dial to 10 amps, and got a draw reading of 2.44 amps. That is huge, is it not? Got this from the neg on the battery to the neg cable which is unhooked.

 

[MBDiagMan]

I wouldn't say it is huge,but it is significant and must be fixed. With the ammeter in place start disconnecting things until the draw goes away or drops to about 100 milliAmps.

Good luck,

 

[vette747]

Ok, I just switched the red wire to the 10 amp setting, and then turned the dial to 10 amps, and got a draw reading of 2.44 amps. That is huge, is it not? Got this from the neg on the battery to the neg cable which is unhooked.

I have 76-77 milliamp on my C4 and I find it high. I know that on a C5 is should not be more than 30 milliamp and it has more computer and other stuff to power.

 

[MBDiagMan]

I have never measured, but I was told a long time ago that 98 millivolts is normal.

Good luck,