Hey, guys...

Fairly new to the Corvette hobby...

I've got a '96 with an LT1 and automatic. I'm the 2nd owner... it's got only 15,000 miles and it's all stock except for the aftermarket radio.

It sits most of the time which hasn't been a problem until my daily driver was in the shop for 2 weeks for a new transmission... so I had to drive the Vette... it wasn't long and the alternator went out and left me with a dead battery in the garage... only symptoms were the turn signals seemed slow at idle (like at a light).

So I charged the battery and drove it to the shop where they replaced it with a GM alternator, but the charge didn't old... it seems there's a current draw on the alarm system remote (which has never worked) and/or the computer.

The battery tests out ok and the alternator tests out ok, or so they say.

Any ideas? Does this sound like a common problem on these cars?

Thanks!

 

Is it the original battery? I had the same problem with my 96 vert. Not a DD, only driven about once a week but when it would sit for two weeks, no start. Had the original battery that would not hold a charge longer than 3 - 4 days. Changed out the battery and have not had a problem since. Good luck.

 

Don't leave the key in the ignition when car is parked, causes computer to draw current and will pull the battery down. Look at side of battery case to see if wet with acid. Overtightening side terminal post bolts is primary cause of cracking the case. Acid on the side can cause a current draw.

 

I agree. If the battery is stock, it's time for a new one. You might want to hold onto it though for NCRS reasons.

The cheapest solution is to purchase a Batttery Tender (brand name). It is a regulated trickle charger that has a built in voltage detector so it will not overcharge your battery. They're about $40.

 

Thanks, guys...

A few answers and little more info...

Battery was replaced in early 2005 with the correct AC Delco unit. It could be defective, as statistically speaking there's always going to be marginal units.

But the shop's saying there's a current draw.

I should also clarify now that it's winter here in the Southern California Coast, this has been a problem since about August, so it's not really temperature related, as I realize that can be a problem with batteries.

Keys are never left in the car (at least at home), but if the key in the ignition draws power, maybe the mechanicals in the ignition switch are suspect? It spent its first 8 years in Florida, but I don't really see any signs of corrosion anywhere (though it's hard to see inside an ignition switch). Maybe there's some sticky bits in there?

 

How about the hood lights?

 

I'm a little rusty on this one now but it was discussed here before a couple of years ago I think. I believe the info we received then was key in the switch signals computer and turns it on resulting in a 250 milliamp current draw. It was also stated even with the key out there will still be a current draw though a much smaller one. don't remember the exact number stated but am thinking it was 80 mills. Need to research it again I guess. I think the source was Gordon Killebrew but I'm not 100% certain of that. Anyway... we have all learned to leave occasionally driven Corvettes plugged into a battery tender to keep it up to full charge.

 

I have a similar problem with a '90 Corvette. It has been that way since I brought it home from the used car dealership - sold as-is. Sometimes it would go dead in one day and sometimes in three days. I stopped it from going dead in one day by pulling out the fuse that causes the interior lights to come on when a door is opened. Afterwards when it is sitting and going dead, the security light is blinking. I found a fuse to pull to make that go off but it won't start with it removed. It's been awhile since I pulled fuses on it and don't remember specifically which fuse it was. I've been disconnecting the battery cable if it is going to sit for more than one day.

 

That is some garage you took your vette to. If they knew about the excess leakage current, then why didn't they find it and fix it? If they know what is drawing the excess leakage current, then have them tell you so someone responsible can repair it. If the remote alarm doesn't work and causes your battery to discharge, then why don't you just unplug the remote alarm?
GM says leakage current should not exceed 50 milliamps. My 87 draws 27 ma.

 

Thanks for all of the info, guys... I'm beginning to wonder if the key switch might be sticky or something.

The underhood lights are shutting off, and that was one of the first things a buddy helped me check. The aftermarket stereo has been eliminated as suspect.

I'm not sure of the amount of drain, but I'll try and find out.

Problem is, with the recent alternator problem I'm thinking the battery may be marginal and I should just replace it... and get a trickle charger setup.

 

Chances are it was just a guess on the excess current. After 2 years in a hot climate a battery is just counting the days as I know being in FL. With a good battery I have no problem leaving the car for a week or two for a business trip, but normally run the car everyday. The current draw should be between 20 to 30 ma.

Making this measurement can be tricky although seems straight forward. After you disconnect the battery to insert the ammeter, the CCM and systems has to come up and be on line normally. Depending on the range of the meter, this may effect the shunt the meter uses for a measurement. In other words you have to pass enough current thru the meter to get the CCM to respond. Using a scale of 100 ma range (depends on meter) or so may not energize the cars electronics and a true reading may not be read.

I had to make this measurement on the 10 amp range with the meter that I used to bring to systems up. Then things responded normal. I could then see the current drawer if I opened a door and when the CCM went into sleep mode and current dropped off. Make sure your key is out, hood light are off as well as all lights to take the final reading.

Using this high range limited me to the resolution on the scale that I could read, but any lower scale that I used, I could not get the CCM and all to come up normally. Possibly a different meter may worked different but due to the fact of what the car demanded on electrical start up dictated the situation. Bottom line is that I could not get the exact milliamp reading but know it was under 30 ma and somewhere in the 20s which was fine. When I woke up the CCM, (key in) I could see the current go up and all looked normal.

I believe that I am in line with what I have read I the Forum where other have taken this measurement also. Never heard of anyone near the 50 ma range. Checking you battery charging is fairly simple. First measure with engine off, should read about 12 volts. Then start engine and measure. Should be about 14 to 14.5 volts. If you get that the alternator appears to be charging normally.