Dead battery on my 1998 C5
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Joined: Sep 2004
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Dead battery on my 1998 C5
I have recently started having trouble with my 1998 C5..the battery is being drained just enough it wont start after sitting overnight. Voltage is down to about 9.5 volts, just enough to click the starter solenoid. It will fire right up with a jump and as I drive I can see it charging at around 14 volts. But let it sit overnight and same thing. I had the local Corvette shop check it out, and they say battery (which was new in January) tested fine, alternator is testing fine, and doing a parasitic test the modules seem to be shutting down, showing only a 22 milliamp drain. They have told me to invest in a trickle charger and learn to live with it...I dont want to live with a car that I have to jump to take for a drive. Does anyone have any ideas?
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Joined: Sep 2004
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I already had the same idea about the shop, but this is the first repair I have had to have on either of my C5's (have 2004 coupe also), and this shop has been around 30 years, I figured they were a good place to start, I guess next time to the dealer.
I am going to try the battery 1st I guess, this is a recent problem, the car doesnt get driven but once a week or so (only 5700 miles) but have never had a problem before, in fact it sat for 2 weeks back in April while on vacation and started up.
My wife drives this one, so I want to make sure she doesnt get left somewhere.
I am going to try the battery 1st I guess, this is a recent problem, the car doesnt get driven but once a week or so (only 5700 miles) but have never had a problem before, in fact it sat for 2 weeks back in April while on vacation and started up.
My wife drives this one, so I want to make sure she doesnt get left somewhere.
5th Gear
Joined: Jun 2008
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Likes: 0
This maybe a dumb idea, but I had the problem so I'll just throw it out there. I had a problem with my battery draining alot. I had the switch on the key fob flipped that when you get near the car it opens the door and when you go away it locks the door. I keep my keys in a drawer above my garage. Here everytime I openned the drawer and closed the drawer, it was unlocking and locking my doors and turning the lights on and off.
Pro
Joined: Sep 2007
Posts: 735
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From: Bucks County Pa
Battery Problems
Hi, it sounds like your battery has sulphated enough so that it doesn't want to hold a full charge. Letting a car sit from week to week is a sure way to ruin a good battery. Some batterys are more prone to not tolerate that kind of driving pattern especially with the vettes heavy draw even at rest. What type battery do you have, and what is the date code on it, was it fresh when you bought it?. I would sincerely suggest you use a proper battery maintainer for that pattern of driving. Take the battery back to the place where you bought it, and have it load tested and replaced with a new fresh one, and use a maintainer when not using the car. It's not that difficult, you can connect it permanently to the battery and run the wire to a spot under the bumper and just plug in the quick connector when you park it. I'm sure you could teach your wife to do it, I taught my wife to handle it, but heck she could probably rebuild the engine to. One other thing you could look at is check the car on a dark nite or in the garage with the light off, and see if any of the interior lights are left on, sometimes the visor or mirror lights are on.
Good Luck
Good Luck
Last edited by bestvettever; Jul 2, 2008 at 05:14 PM.
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I figured out the keyfob deal as soon as I bought the car and disabled it..its more annoying then helpful. The battery is an OE ACDelco. Last night it held its charge overnight. the DIC reads 11.6 volts before startup now and 13.5 to 14 when driving. The parasitic drawl test showed less than 20 milliamps. either a loose connection was tightened in the shop when they were testing, or else its intermittent. Today it ran like a champ again. I will see what happens! if it starts again i will swap the battery and get a battery tender i guess.
Racer
Joined: Jul 2003
Posts: 463
Likes: 2
From: Mishawaka Indiana
Mine just did this last week. I would hear a faint click every 30 seconds or so and couldnt find it. Well after 2 days it killed the battery after sitting for only about 8 hours. Come to find out the pass power seat rack was trying to move its self and drained the battery. When I caught it the front motor was so hot I burned my thumb on it. I was real lucky it didnt burn the car to the ground. 
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Pro
Joined: Sep 2007
Posts: 735
Likes: 7
From: Bucks County Pa
Batery Problems
I figured out the keyfob deal as soon as I bought the car and disabled it..its more annoying then helpful. The battery is an OE ACDelco. Last night it held its charge overnight. the DIC reads 11.6 volts before startup now and 13.5 to 14 when driving. The parasitic drawl test showed less than 20 milliamps. either a loose connection was tightened in the shop when they were testing, or else its intermittent. Today it ran like a champ again. I will see what happens! if it starts again i will swap the battery and get a battery tender i guess.
Good Luck
Last edited by bestvettever; Jul 2, 2008 at 11:27 PM.
Instructor
Joined: Feb 2006
Posts: 242
Likes: 22
From: Saint Charles MO
battery
I was having the dead battery problem with my 2000 vert.
The battery was 2 months old when I bought the car.
Lived with the problem for a while and tested the draw current after the BCM went to sleep and figured out it was a bad battery (not a drain on the battery). Replaced it with an Optima red top and no more problems.
The battery was 2 months old when I bought the car.
Lived with the problem for a while and tested the draw current after the BCM went to sleep and figured out it was a bad battery (not a drain on the battery). Replaced it with an Optima red top and no more problems.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Actually a good charged battery should read 12.5 ~ 12.6 volts across the terminals. If it's at 12.2 it's already about 30% discharged. A totally discharged battery (meaning it won't power much at all) will show 10.5 volts.
The DIC on the C5 usually reads about 0.3 ~ .05 volts less than the actual terminal battery voltage. If you have a voltmeter then check directly across the battery terminals for the best measurement.
The DIC on the C5 usually reads about 0.3 ~ .05 volts less than the actual terminal battery voltage. If you have a voltmeter then check directly across the battery terminals for the best measurement.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Do this test. Charge the battery fully. Measure the terminal voltage with a meter. If it's less than 12.5 the battery is weak. Let the car sit for 4 or 5 days and measure the voltage once a day and record it. If it drops more than 0.2 volts in a few day its toast.
Drifting
Joined: Sep 2003
Posts: 1,363
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From: 1994 LT1 Coupe 6-speed with FX3 & 2000 LS1 Vert 6-Speed with F45 Hunterdon County, NJ
Actually a good charged battery should read 12.5 ~ 12.6 volts across the terminals. If it's at 12.2 it's already about 30% discharged. A totally discharged battery (meaning it won't power much at all) will show 10.5 volts.
The DIC on the C5 usually reads about 0.3 ~ .05 volts less than the actual terminal battery voltage. If you have a voltmeter then check directly across the battery terminals for the best measurement.
The DIC on the C5 usually reads about 0.3 ~ .05 volts less than the actual terminal battery voltage. If you have a voltmeter then check directly across the battery terminals for the best measurement.
with everyone's assessment that it sounds like the battery could be the problem.However, here's a subtle correction to battery voltages and their translation to percent of charge:
A battery at rest (24 hours since last charging cycle) and with no drain (battery terminal disconnected) should read as follows:
12.6 - 12.65 == 100% charged
12.4 == 75% charged
12.2 == 50% charged
12.0 == 25% charged
11.8 or less == 00% charged, or bad cell(s)
each 'cell' contributes 2 +/- volts to the overall battery voltage.
Therefore, for example, should a battery read 10.5, it implies one 'cell' has shorted-out (plate material fallen to the bottom of the cell) -- i.e. time to replace the battery.
However, remember you cannot use the DIC voltage reading to accurately determine the battery charge state -- as it could never read 12.6 volts, even if the battery is 100% charged, as once the key is turned, multiple systems are energized (ignition, fuel pump, etc).
Drifting
Joined: May 2000
Posts: 1,917
Likes: 3
From: Southern NH
11.6 volts on the DIC is not good for a charged battery. Your parasitic draw is normal ... no problem there.
Do this test. Charge the battery fully. Measure the terminal voltage with a meter. If it's less than 12.5 the battery is weak. Let the car sit for 4 or 5 days and measure the voltage once a day and record it. If it drops more than 0.2 volts in a few day its toast.
Do this test. Charge the battery fully. Measure the terminal voltage with a meter. If it's less than 12.5 the battery is weak. Let the car sit for 4 or 5 days and measure the voltage once a day and record it. If it drops more than 0.2 volts in a few day its toast.
To properly diagnose the battery you need to measure the voltage at its terminals with a DMM. As noted above, a fully charged battery will read ~12.65V and a dead battery will read anything under 11.8V.
With the engine off and a DMM on the battery you can run a load test by turning on your high beams and watching the battery voltage which should drop but stabilize. The important thing is after a minute or so turn the highbeams off and see if the battery returns back to near it's original voltage after a few minutes. If it doesn't after even 10 mins then the battery is having trouble holding its charge.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
This is not a correct statement. The DIC voltage is designed to measure the alternator output, not the battery voltage. 11.6 on the DIC is perfectly fine before starting the car since it's not measuring the battery at the terminals. Once started, the DIC should read in the 13 - 14.5V range as it's measuring the alternator output.
Drifting
Joined: May 2000
Posts: 1,917
Likes: 3
From: Southern NH
If that's the case, then why does the DIC voltage show ~ 0.5 volt less than the battery terminal voltage while the car is running? - I've tested it many times. Wouldn't you think the alternator voltage would actually be slightly higher (or at least the same) than the battery terminal voltage since it has to push current to the battery?
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Once the engine is running, the voltage at the battery terminals is the same as the alternator output but if you look at the schematics of the circuit the DIC gets it's data from a serial line to the PCM that gets the data from a separate circuit on the alternator that provides 2 readings (F Term and L Term). Without going into detail you can see that the DIC does not get it's data directly from the battery circiut which explains the differences.
Advanced
Joined: Jul 2012
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I know it's an old thread, but for me it got progressively worse over the years and it turned out to be the ******* passive key fob in the 1998/1999. Just replace it with a non-passive one, and deactivate the old one, battery draining problem solved.
Last edited by nuts105; Dec 4, 2018 at 12:35 AM.
