Electrical problem and cause?
Thread Starter
Instructor
Joined: Jan 2005
Posts: 141
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From: Mt. Zion Central Illinois
Electrical problem and cause?
I have a 2005 and in the winter (central Illinois) I start it and run it every week. Today I started it and the voltmeter and DIC indicated 14.8 volts. Ran it down the road for an hour and the indicators stayed at 14.5v unless at idle and then read 14.0v. Taking it in Monday but wondering if its a battery not accepting a full charge or regulator output staying too high. Anyone with the same experience? C'mon SPRING!!
Safety Car
Joined: Jul 2004
Posts: 3,867
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From: Wantagh,L.I. New York
I have a 2005 and in the winter (central Illinois) I start it and run it every week. Today I started it and the voltmeter and DIC indicated 14.8 volts. Ran it down the road for an hour and the indicators stayed at 14.5v unless at idle and then read 14.0v. Taking it in Monday but wondering if its a battery not accepting a full charge or regulator output staying too high. Anyone with the same experience? C'mon SPRING!!
Melting Slicks
Joined: Feb 2005
Posts: 3,380
Likes: 103
From: Visalia CA
thats pretty normal, battery will always read highest after a cold start. It's a 12 volt system, anything over that and you are good to go. A wasted trip to the dealer, unless you want some free cheap coffee 
Burning Brakes
Joined: Oct 2006
Posts: 1,011
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Well, that really might be an indication of a battery with a problem.
I've got a rather heavy duty charger. It will output 40amps or something like that.
If I charge a battery and it takes a huge charge and never starts to 'taper down', after something like 30 minutes; or if a battery takes no or very little charge (when it obviously does not have the power to start a car) for about the same 30 minutes; either of these usually means the battery is toast. Buy a new one.
A battery that still has life, but is just discharged, should take a high amp charge at first, then start to taper down, and finally should drop down to almost zero.
Also, if you do get a battery to take some charge, and it might even start a car, but you measure the voltage at the battery and it is less than 12volts - the battery probably has a dead cell and should not be trusted. It's going to be dead again shortly.
But remember - the alternator in a car has 'temperature correcting' logic in it. If your outside temperature is low, the alternator is going to throw more voltage at battery, because it needs a higher voltage to charge it. In general, you will see lower voltages out of the alternator in summer than in the winter.
I've got a rather heavy duty charger. It will output 40amps or something like that.
If I charge a battery and it takes a huge charge and never starts to 'taper down', after something like 30 minutes; or if a battery takes no or very little charge (when it obviously does not have the power to start a car) for about the same 30 minutes; either of these usually means the battery is toast. Buy a new one.
A battery that still has life, but is just discharged, should take a high amp charge at first, then start to taper down, and finally should drop down to almost zero.
Also, if you do get a battery to take some charge, and it might even start a car, but you measure the voltage at the battery and it is less than 12volts - the battery probably has a dead cell and should not be trusted. It's going to be dead again shortly.
But remember - the alternator in a car has 'temperature correcting' logic in it. If your outside temperature is low, the alternator is going to throw more voltage at battery, because it needs a higher voltage to charge it. In general, you will see lower voltages out of the alternator in summer than in the winter.
Le Mans Master
Joined: May 2005
Posts: 5,865
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From: Hope, Arkansas - '07 LMB Coupe
Cruise-In VIII Veteran
Once the engine is started, the volt meters are showing the voltage output of the alternator, not the battery. To see the true battery voltage, you have to shut down the engine and go into accessory mode.
Race Director
Joined: Oct 2004
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Actually, you have to go into Ignition On Engine Off mode. That requires holding Accessory down for 10 seconds. Then you can use the digital readout in the DIC to see battery voltage.
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Thread Starter
Instructor
Joined: Jan 2005
Posts: 141
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From: Mt. Zion Central Illinois
Just went out and checked the battery voltage in the ACC mode. It was reading 11.7 volts. Car started and went to alternator output of 14.5 volts at idle. Based on the 11.7v reading and never having seen a charged battery read less than over 12 volts, I'm pretty sure that the battery is bad. Will post results on Monday the 5th after dealer checkout.
Burning Brakes
Joined: Jul 2006
Posts: 819
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From: Chambersburg pa.
What your seeing is when the alternator is cold the coil resistance is lower. The resistance of copper is directly proportional to temperature. So when the copper is cold it's resistance is lower, when the copper in the alternator coils heat up the resistance increases. So the voltage follow this pattern. This can also happen if your loading the alternator with alot of electrical accessories. This is norminal for the alternator / regulator to act this way. 
Burning Brakes
Joined: Oct 2006
Posts: 1,011
Likes: 6
11.7 volts. A 'good' battery puts out 2.1 volts per cell and it has 6 cells, in series. Therefore, 12.6 volts is what a 'good' battery should indicate. (No alternator running, no significant load, not significantly cold, etc.) I don't know how accurate the DIC display is for battery voltage. A decent multimeter used directly on the battery post would be better.
Your battery probably has some life left in it, but is probably getting 'old'. Just how much do you worry about the car? The battery could be 'load tested' for a better indication of it's condition. With a Corvettes (and most cars) loads of electronics, I would not run this test while the battery is in the car.
Your battery probably has some life left in it, but is probably getting 'old'. Just how much do you worry about the car? The battery could be 'load tested' for a better indication of it's condition. With a Corvettes (and most cars) loads of electronics, I would not run this test while the battery is in the car.
Race Director
Joined: Oct 2004
Posts: 10,089
Likes: 14
Just went out and checked the battery voltage in the ACC mode. It was reading 11.7 volts. Car started and went to alternator output of 14.5 volts at idle. Based on the 11.7v reading and never having seen a charged battery read less than over 12 volts, I'm pretty sure that the battery is bad. Will post results on Monday the 5th after dealer checkout.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 141
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From: Mt. Zion Central Illinois
Based on past expierience I'm sure the battery is almost gone. In fact I'll bet my warranty on it!! If it was out of warranty I'd go with the Optima, but since it isn't it looks like another Delco. Thanks to everyone that replied. Monday I'll post the results.
