Battery Drain-Down Problem...

[HammerDown]

Hi people, been a while since I've visited.
Besides the regulator/reluctor sticking in the alternator, is there anything else that will drain my battery down in my 81 Vette?

I know the radio has a memory and the car's computer (may) draw something but, if I'm NOT seeing any lights on etc when the car is off what could be killing the battery in a few days of sitting?

Note...7/09 I did replace the alternator because it WAS draining the battery. I diagnosed this by killing power to radio, internal lights etc...then...removing the + battery terminal and noticing a small spark when reattaching it. I then did the same test with the +alt wire removed > no spark at the +battery.

Now, once again the 4 month old re-manufactured alt is doing the same thing???

 

[TimAT]

Did you run the same test this time as you did last time? same result? Not unheard of for a regulator or diodes to go bad. Not that fast, but it's possible.

The regulator is a solid state- no moving parts. But a voltage spike can do it in too.

 

[HammerDown]

Did you run the same test this time as you did last time? same result? Not unheard of for a regulator or diodes to go bad. Not that fast, but it's possible.

The regulator is a solid state- no moving parts. But a voltage spike can do it in too.

Hi Tim, after some disbelief the current rebuilt alt could be doing the same thing I did go through the same test again. Sure enough with alt + hooked up and the +battery wire is removed then touched to the battery it tosses a small spark...unhook the alternator and no spark at the battery.

I know the manager at Pep Boys and he did order me another alt. Too bad their testing machine doesn't show this specific problem, it only shows that it is infact charging and "good". I thought at 15 volts it was charging a bit too much!

Hope this next alternator lasts longer then 4 months.:eyerole the other one lasted 10 years.

Thanks for the feedback, Ray

 

[6880 Mike]

Check the light on the vanity mirror. My fiancee had a slow drain in her '96. We eventually found the vanity mirror light was on.

 

[HammerDown]

Check the light on the vanity mirror. My fiancee had a slow drain in her '96. We eventually found the vanity mirror light was on.

Yep...I checked that, it's off.

 

[73shark]

Unless you really like changing out alternators, cut your losses and buy a new AC-Delco alt. My experience w/ remans is that they from overseas and mostly junk.

 

[HammerDown]

Unless you really like changing out alternators, cut your losses and buy a new AC-Delco alt. My experience w/ remans is that they from overseas and mostly junk.

Good point, however it's under warranty so...I'm only out a little of my time.
Maybe reman #2 will be the charm

 

[HammerDown]

Good point, however it's under warranty so...I'm only out a little of my time.
Maybe reman #2 will be the charm

Second alternator's in...something tells me I have a draw from somewhere else > maybe the computer isn't going into idle mode after the car is shut off

 

[Rookie Vette owner]

Second alternator's in...something tells me I have a draw from somewhere else > maybe the computer isn't going into idle mode after the car is shut off

This is new to me, What is "computer idle mode"! I have a drain I've been chasing on my 82' for a while, I have already found a faulty "courtesy light" module that left lights on all the tiime, but that's fixed and the problem remains!

 

[HammerDown]

This is new to me, What is "computer idle mode"! I have a drain I've been chasing on my 82' for a while, I have already found a faulty "courtesy light" module that left lights on all the tiime, but that's fixed and the problem remains!

From what a mechanic/corvette specialist friend told me, on (my) 81 the computer stays live for a few moments after the engine is shut off...then goes into idle mode, no draw from the battery.
Not sure if that's my problem yet...for me electrical issues is a real PITA. :bash

 

[Rookie Vette owner]

I know what you mean about a pain! I had mine drain down in a couple of minutes after a 20 minute drive. I figure the battery was old and weak so I replaced it. I have since placed a cut off on it also, but the problem is still there. I did a run of pulling the fuses, but never got through all of them, so I need to start over. Good luck on your hunting, and if I find anything I'll try to pass it along in the hopes that it may help you or someone else! Enjoy the rest of turkey day!

 

[HammerDown]

Fixed it...hooked up a battery-tender :L
It holds it at 12.72v


I can easily tear into a V-8 and make it right but damn I HATE electrical issues

 

[69_coupe]

Fixed it...hooked up a battery-tender :L
It holds it at 12.72v

A battery-tender don't fix the drain, you have only "bypassed" the problem. If you remove the positive terminal and hook up a volt meter between the cable and the battery terminal it will show battery voltage until the drain is fixed. Disconnect one circuit at a time until the volt-meter drops to zero, and yes the alternator may be the problem. When you can't read battery voltage at the volt-meter anymore the drain is gone. (remember that a clock or radio with memory must be disconnected) The spark test can be dangerous. If the drain is big enough to cause a spark, an old-school test lamp will probably do the trick. Connect it between the cable and battery terminal, if there is light it's a drain.

 

[Bobsvette]

Why can't it be something as simple as a bad cell in the battery?

 

[69_coupe]

Why can't it be something as simple as a bad cell in the battery?

It can, but not if it makes a spark... But some amplifiers, CD changers and some other equipment will draw a small current when you connect the battery, and hence create a small spark, so you can be right.

 

[HammerDown]

A battery-tender don't fix the drain, you have only "bypassed" the problem. If you remove the positive terminal and hook up a volt meter between the cable and the battery terminal it will show battery voltage until the drain is fixed. Disconnect one circuit at a time until the volt-meter drops to zero, and yes the alternator may be the problem. When you can't read battery voltage at the volt-meter anymore the drain is gone. (remember that a clock or radio with memory must be disconnected) The spark test can be dangerous. If the drain is big enough to cause a spark, an old-school test lamp will probably do the trick. Connect it between the cable and battery terminal, if there is light it's a drain.

Thanks for the above info...I know it ain't fixed and the battery float/tender is only holding it a 12.52v after 2 days of sitting. I'm trying not to hurt this "new" battery.
It should hold 12.62 to 12.72 to keep it healthy.

I'll try to diagnose it a little more with your suggestions. I have a high dollar Blue Point meter just green on how to really use it to it's full potential.
As mentioned prior, I can mic, rebuild anything with pistons but digging into wires and circuits makes me crazy. :W;help

 

[jetset0045]

Hey hammerdown, i hear you, i hate electrical problems...

I just went through something similar with my 74 vette...battery would drain after 3 or 4 days of sitting....other than that, no symptoms...did an inline test from the battery and found a .45 amp constant draw, even after going through and removing fuses one by one....

long story short, someone i bought the car off of had put on a new alternator, cut the plug off, and reversed the wires when they re- connected it!!....i never would have guessed this, and it took a lot of head scratching to figure out!...but there it was....

 

[Lib]

Timely discussion for me. Replaced battery in our 74 C3 about 3 weeks ago and took it for a 3 hour drive, then parked it. Went to drive it last Friday and.....click. Put the new battery on charge and reinstalled it yesterday (reading 12.68v), went for a 1 hour drive with no significant loads (a/c, lights, etc.) turned on, parked it, and immediately put the meter on the battery. Down to 11.7v. Obviously not charging sufficiently when running, even though the dash instrument shows it is charging. I will have time this weekend to test the alternator, etc. I'll continue to watch this thread and input soon with findings.

 

[daleman]

Battery drain

From what a mechanic/corvette specialist friend told me, on (my) 81 the computer stays live for a few moments after the engine is shut off...then goes into idle mode, no draw from the battery.
Not sure if that's my problem yet...for me electrical issues is a real PITA. :bash

My battery went out in my 82 over the holiday also. As it turns out, once I installed the new battery, I could here a faint hum comming from the back of the car. I believe this to be my fuel pump. I had just replaced my Oil Pressure Guage, and some how they are related. I am still trying to figure out how to stop it. You might try sitting in your car with everything turned off. Mabe you have the same issue.:ugh

 

[tcxd40]

I with y'all on this battery drain issue.

Started my '81, which is being rebuilt, two weeks ago everything worked fine. Got it ready for the body shop today and it won't start. Battery won't turn it over however the battery tests fine, ?????