Charging Issues 2008 Corvette

JBruno88

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Hey guys, I'd like to get some thoughts on some charging issues I experienced tonight.

I was on the way home from GLD to oak brook tonight when a message came on in the dash saying to service charging system. I was watching the battery voltage the whole way home and steadily dropped from 14v all the way to 7v when the car finally died in my garage.

My initial thoughts is the alternator, but what's the best way to be certain? I can pull the battery and charge it and then have it load tested to rule that out and check all connections/grounds.

This happened after 2 back to back passes in the 1/4, let the car sit while I swapped to street wheels. I did load a new tune before the two passes, but only changed shift points with hp tuners.

Any other thoughts? Thanks in advance.
 

rocket5979

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The simplest home test would be to put voltmeter directly on the positive and negative terminals of the battery (or underhood + & - terminals). Measure voltage while the car is at rest. Then start the car, let it idle, and see where the voltage sits. You should see about 12.5 volts at rest with a fully charged battery and anywhere from 13.5-14.5 volts with the car running. The key is that the voltage should increase by at least a volt or two after the car is started. If voltage stays the same or drops then you know that something is wrong with your charging system, which could be the alternator itself, a loose connection, etc.

Any local Autozone or Oreillys will do these tests for you for free by the way.
 

Stink Star Productions

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What is the condition of your battery? It's just as likely a fried cell in the battery won't allow the alternator to properly charge it. Other than that, the alternator seems like the only other logical thing that may be wrong with the car
 

boostedguy05

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Easiest way to check it is to take it to a parts store like stayed above and have them load test it. I used to get that message all the time in the grand prix. If it was raining and i had wipers on, headlights on, radio on, it would go off. Had a dealer look at it and "everything checked out okay". Eventually I replaced the battery and have been fine.
 

JBruno88

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Thanks for the info, I'm going to jump start the car today after work to get it to the parts store.
 

EmersonHart13

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Another vote for the store, they can check both. Free and easy!
 

JBruno88

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Yeah the problem is getting the car to the parts store. In regular stop and go traffic I'm pretty sure the car will die within 2 minutes and there is also the dilemma of getting the battery charged back up to even be able to attempt to make it there.

I got beers and food for anyone who is able to come give a guy a hand tonight if you have the equipment to test the battery/alternator.
 

TCG Member 5219

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Similar thing happened to my c6 when the blower went on. I would get service charging system all the time when sitting at idle. Turned out to be the TR6 plugs were the problem. They are known for causing low voltage. Something with the copper causing higher resistance or something. The fix was to put in the colder OEM ZR1 plugs. The car idled perfectly with no more messages, and the voltage never would budge again. The irridiums are better. This may not be your issue, but its an issue with these cars. Your issue is likely alternator or the like, but Im sure if you are running the TR6 plugs, it was adding stress to the charging system. Just my experience. And it was my tuner who said it was an issue. He said it was common on the Tahoes too.
 

TCG Member 5219

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Thanks for the info, I'm going to jump start the car today after work to get it to the parts store.
Oh and FYI the C6 will not run properly without a fully charged battery even if the car is running and the alternator is working properly. These cars are so finicky with voltage.
 

EmersonHart13

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Just pull the battery and alt and bring them in? They don't need the car to test them...
 

billzrx7

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Alternator is shot. the easy test is to start the car and unplug the negative off the battery. it will most likely die immediately as theres no longer any electricity in the system. Ever read a battery and itll say something along the lines of backup time (I forget how they phrase it) but its usually in minutes, thats an estimate on how long that battery will power your car before it is completely discharged.
 

Turbocharged400sbc

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Similar thing happened to my c6 when the blower went on. I would get service charging system all the time when sitting at idle. Turned out to be the TR6 plugs were the problem. They are known for causing low voltage. Something with the copper causing higher resistance or something. The fix was to put in the colder OEM ZR1 plugs. The car idled perfectly with no more messages, and the voltage never would budge again. The irridiums are better. This may not be your issue, but its an issue with these cars. Your issue is likely alternator or the like, but Im sure if you are running the TR6 plugs, it was adding stress to the charging system. Just my experience. And it was my tuner who said it was an issue. He said it was common on the Tahoes too.

irdium "resister core" plugs with the dissimilar welds, cant possibly be lower resistance than "resister core" copper plugs, and how the fuck would anything on the secondary side of the coil (firing at 35+ kv and really low current) be affecting the charging system?

id bet it had more to do with being close to the alternator rpm cutoff where the pcm kills the field to help keep the engine running. just a 25rpm bump on your field control table will fix that too.

the line he was feeding ya on the plug resistance is fucking hilarious

Alternator is shot. the easy test is to start the car and unplug the negative off the battery. it will most likely die immediately as theres no longer any electricity in the system. Ever read a battery and itll say something along the lines of backup time (I forget how they phrase it) but its usually in minutes, thats an estimate on how long that battery will power your car before it is completely discharged.
yeah, in the olden days, id suggest that....on these new cars there is far too much chance for current backfeeding and other nightmares to surface doing something like that.

far better to check charging voltage...and see how it changes as you turn on all the lights/defroster/heater fan etc.

if your battery is still the oem from 08, then id say get a new one, but its probably the alternator, they eat bearings for lunch and the commutator bounce kills the brushes real quick
 

TCG Member 5219

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irdium "resister core" plugs with the dissimilar welds, cant possibly be lower resistance than "resister core" copper plugs, and how the fuck would anything on the secondary side of the coil (firing at 35+ kv and really low current) be affecting the charging system?

id bet it had more to do with being close to the alternator rpm cutoff where the pcm kills the field to help keep the engine running. just a 25rpm bump on your field control table will fix that too.

the line he was feeding ya on the plug resistance is fucking hilarious



yeah, in the olden days, id suggest that....on these new cars there is far too much chance for current backfeeding and other nightmares to surface doing something like that.

far better to check charging voltage...and see how it changes as you turn on all the lights/defroster/heater fan etc.

if your battery is still the oem from 08, then id say get a new one, but its probably the alternator, they eat bearings for lunch and the commutator bounce kills the brushes real quick
You are probably right, but the irridium plugs did fix my issue.
 

boostedguy05

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take parts off of vette.
put parts in cobalt.
run to parts store for testing.
buy replacements as needed.
 

bikrboy128

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how old is the battery? is it the original? i would suggest taking the battery out of the car and over to the parts store. theyll load test it and tell you if you need a new battery. i wouldnt try and drive it to the store with the system discharging.if it is a bad battery you're putting more load/wear and tear on the alternator that's trying to charge a bad battery and run the car.
 

Ti28

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If it's the OE battery, replace it. And sounds like your alt crapped out. Replace alt and battery and have a merry day.
 

JBruno88

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Original battery. Going to do some testing when I get home, but most likely I'll be replacing the battery and alternator.
 

EmersonHart13

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08 GM battery? Definitely ready for replacement. They aren't known for their longevity...
 

JBruno88

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Car had less than 10k on the clock and the battery sat on a tender when not driven, but regardless it'll probably get replaced
 

P40E

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If an alternator stops charging , the first thing you will see is the volt gauge on dash reading at 12.6v while engine is running (Which is battery voltage) .

Then the car will run off the battery until the voltage is too low to run the car . You will see this happen on the volt gauge as the voltage gets lower and lower and lower . Then car will die out .

If you have drained the battery down , it is still ok to recharge it . Just because a battery is half drained doesn't mean its bad now . That's what batteries are designed for . To constantly be recharged . You can trickle charge it yourself .

Or if you get the alternator replaced and it's charging again
You can jump start the vehicle and let the car recharge it .

Just don't go driving around and shut the car off somewhere before the battery is at full power . Wait till least strong enough to start the car when cranking .
 

JBruno88

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If an alternator stops charging , the first thing you will see is the volt gauge on dash reading at 12.6v (Which is battery voltage)

Then the car will run off the battery until the voltage is too low to run the car . You will see this happen on the volt gauge as the voltage gets lower and lower and lower . Then car will die out .
This is exactly what happened.
 

P40E

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how old is the battery? is it the original? i would suggest taking the battery out of the car and over to the parts store. theyll load test it and tell you if you need a new battery. i wouldnt try and drive it to the store with the system discharging.if it is a bad battery you're putting more load/wear and tear on the alternator that's trying to charge a bad battery and run the car.
You can not tell if a battery is bad unless it is fully charged first . Then you do a load test on it to determine if it can handle a load . The minimum is usually 9.6v during a load test . A bad battery will crash hard and fast during a load test if it can't handle a load .

Again , the battery did not cause your charging problem . A bad battery will not make the volt gauge read low when the car is running . Because the gauge reads current voltage . If a car is running and alt is charging the gauge will show charging voltage usually 13+ to 14+ .

His battery is low because the car drained it cause it ran off the battery to stay running . Then it was too low for even that .

The beginning signs of a battery going bad are slow cranking issues . That's when the battery gets hit the hardest , when the starter is putting a load on it . The alt will recharge the battery when the car is running . But eventually the battery will not be able to hold the charge . And the car will be slow cranking on start up.
 

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