Dear corvette fans

I have C5 corvette 1998 and have the problem that whenever I leave the car in the garage for a week the battery goes down to 5V!

If I then charge it the car runs fine and the battery is at 11.9V a day later. It seems that the battery is slowly decharged during a few days. Last year before I had the corvette for 6 month in the garage (battery was taken off and regularly charged) I didn't have any such problem. And I didn't change anything in the car.

I have already checked whether any lights etc. are on - switched off everything.

Do you have any idea what the slowly discharging could cause? Thanks a lot for your help.

Best regards,
C5-CH

 

Mynocks.

 

Clean the ground points, this is most often the culprit

Peace
Chip

 

Okay, thanks for your hint. Do you have a list where all the ground pins are? thx

 

Try the weights and measures sticky at the top of the page. (It's in the very first post)

or

Use the search for hundreds of threads

Should fix your issue,

Also, just because the battery takes a charge, does not mean the battery is good

Peace
Chip

 

How old is the battery?

 

Disconnect the battery,check the voltage.
Leave it disconnected,give it a day or 2 and check the voltage again-if the voltage still drops,bad battery.
No use investing a bunch of time checking the car over,until you make sure the battery's ok.

 

If you still have the original battery, I would change it. These cars need a good strong battery for everything to work properly. Believe me, I know. A 9 year old battery is a ticking time bomb.

 

Perhaps a new battery is in order after the terminals are cleaned and checked thuroughly!

The in the best interest of keeping the battery charged while sitting (Our Vettes are notorious for draining them as the sit) you need to get a battery tender!

It is what I use and many others do as well! I got mine at Harbor Freight and it has worked flawlessly for 3 years!

Thanks,matt

 

Dear all

Thanks a lot for your help. My battery is 8 years old (a red top) and the voltage is still at 12.5V after 2 days - if not connected. On the other hand the current is 34mA if the car is not running, so this should be okay.

In any case I will buy a new battery since I agree with you that it is not worth examining the whole car and spending a lot of time only to find out in the end that the battery isn't good enough anymore.

Best regards,
C5

 

as mentioned, start with the battery and move on from there

 

If it's not the battery, you can diagnose the problem by testing current across the fuses - one at a time. Figure out what is drawing power with the car off. Go from there.

 

My guess is that an 8 year old battery has just reached the end of its life even if it is holding charge without the slight drain.

Heres an old post I made which might help:

Identifying Battery Problems
The C5 eats batteries unless you take some regular precautions. If your battery continually dies its either the battery which is on its last legs or something on the car.

You also need to look at how you use the car. Is it a daily driver? If so the battery should be getting a good top up every day so you may have a problem.


Is it a DD but you do short trips? If so you'll be taking a lot out of the battery every time you start. For a short trip, say less than about 20 mins, you won’t top it off properly. Eventually it'll drain.

Is it a weekend car. If so, this car eats batteries. Theres a 20MA drain even dormant. If you dont drive the car for a reasonable time every week or so, it'll kill the battery. In this case you really do need a battery tender.

You’ll know when your battery is bad. As it gets low you may get strange electrical indications (random warnings and U fault codes). As it gets lower it may drop the memory settings or defaults such as HUD settings. Eventually you’ll get the dreaded chattering relays in the footwell and eventually the lights on the IPC will disappear.

Most batteries can be recharged quite successfully, although AGMs are harder. Start by checking the charge on the battery. Don’t read the DIC when the car is off. The value you see on the DIC is alternator output when the car is running. It will always measure an inaccurately low voltage on the battery when the ignition is off and figures of 11.0V to 11.9V is normal in this case. With the engine on, the voltmeter should show between 13V and 14.5V. You need to measure voltage across the battery terminals using a digital multi meter if possible. A fully charged battery measures 12.7V and a fully discharged battery measures 11.9V. Partially discharged batteries will give a reading somewhere in between.

If the battery is low give it an overnight charge (or put it on a battery tender until you get a fully charged indication) and retest it. A true test is under load and Autozone will do that test for free.

If you’ve recharged it and it still runs down, then you need to start looking for excessive drains. Bill Curlee posted a good method for checking:

http://forums.corvetteforum.com/1567522286-post590.html

There are some common faults which are well known for causing problems:

First to check is the interior lighting rotary switch on the drivers panel. It’s possible for that to be turned on as there’s a setting (fully clockwise) which bypasses the auto off function. Turn it fully counter clockwise and check after about 30 mins (preferably in the dark) that the interior lights have gone off.

If it’s not the lights something has failed or is badly installed.

Have you fitted an after-market device which draws current? Typically it’s a cellphone charger, radar warner or a similar device that’s the problem.

If still no joy, you need to start pulling fuses to identify the problem.

The power seat switches on the side of both seats are notoriously unreliable. The switch becomes sticky with use and can stick in the “on” position. You shouldn’t damage the motors as they are thermally protected. The fuse may blow so worth checking (Fuse 36 20A in footwell).

The driver’s lumbar motor can also cause issues so check this too (mini fuse 3 15A in footwell). The seat controls connect under the seat. Pull the connector and if the drain stops that’s your problem.

Less common but not unheard of are failures of the headlight motor control module the alternator and the Bose Amplifier under the dash on the driver’s side.

 

Thank you very much for this helpful explanations. I am sure now that the battery is at its last leg.

I use the car at most every second weekend, sometimes it is in the garage for 4 weeks. Thus the battery has been killed.

Is there a specific battery tender that you can recommend? thx

Best regards,
C5-CH

 

This CTEK is the one you want

http://www.customcorvetteaccessories...rycharger.html

Peace
Chip

 

Whew . . . .thanks for typing all that out DeeG, it gets repetitive every time it comes up

And I second the rec on the Ctek...excellent charger/maintainer, plug in and forget.

 

Try looking in this thread - tons of info on the C5 electrical system by forum member Bill Curlee and a cast of many:

http://forums.corvetteforum.com/c5-t...tion-long.html