I went on a fun ride last sunday with about 300 other vettes. I was getting ready to leave and my volt gauge was dropping to 11.2 volts up to 12.9 while idling. I go to leave and it stalls, start stall, then pull key wait 10 seconds, I did this the car started and kept dropping in the voltage as before while idling. I finally got it on the road and the volts stayed up to where they always do since I've owned the car at 13.5-13.7 volts while driving. Then one time I was getting on it hard and it like cut out dash lights kinda flickered and then it caught it self and kept going. Is this a battery problem or alternator? I haven't checked them yet, but thought I would ask here. It does have a red top Optima installed.

Here are the codes I pulled and they are history codes: 10-PCM: P1431H..AO-LDCM: U1064H..A1-RDCM: U1064H..these were the only codes present.

Update today 11-02-13: I went to drive my car yesterday and the battery was dead after sitting about two weeks. I charged the battery (red top optima) and took it to Auto Zone to have it load tested. Battery had 12.5 volts when I checked it after charging. The test was done and the guy doing the test said the battery is 83% charged under the load and the battery is good. Any comments on this test or does this seem right. I am going to check the alternator after putting the battery back in. I should get a higher voltage check at the battery if the alternator is working correctly, while the car is running. If the alternator is not working correctly I should get a lower voltage reading. Is this correct. Sorry for the long post and so many questions just want to get this figured out. If every thing checks ok, then onto the ignition switch.

Update today 11-03-13: Hooked up the battery this morning and checked the alternator output at the battery was 14.75 Volts and checked at the alternator was 14.9 Volts. So I guess the alternator is good. Start checking the ignition switch now. Could it be that it not being started or driven in a couple of weeks drain the battery if not to start. May look into getting battery charger for it when sitting that long.

 

Did you pull the codes while the car was still running to see if any are current or after you shut it off? Not home now so I don't know what they all are.

If I recall, the ignition switch can also give these symptoms also.

 

Could be either. Have the battery charged and load tested. Most parts stores will do this free. I think they will also check the alternator or it is easy to do yourself with a meter. Make sure the connections are clean and tight.

 

Definitely add the ign switch to the suspect-list.

 

Codes were pulled on the posted date. No other codes showed, only the ones listed.

 

Anything specifically I should check as far as the ignition switch goes.

 

Bill did an article that's in the sticky up top. He shows what goes to pot and how to fix it. I'd link to it but I'm stuck on my phone.

 

I had a similar problem and it ended up being an extremely loose ground on the engine block (between the headers and starter). Tightened her up and all was good

 

Much goes through the ignition switch, and its malfunctions due to toasty (multiple) contacts inside, cause voltage drops that wreak havoc.

BC's treatise on the subject is excellent and loaded with pix.

 

Here is the link to Bill's info on the ignition switch:
http://forums.corvetteforum.com/c5-t...ch-repair.html
The U1064H code is Loss of Comm with BCM. Could be related or separate, but is worth investigating...
Let us know what you find...

 

I went to drive my car yesterday and the battery was dead after sitting about two weeks. I charged the battery (red top optima) and took it to Auto Zone to have it load tested. Battery had 12.5 volts when I checked it after charging. The test was done and the guy doing the test said the battery is 83% charged under the load and the battery is good. Any comments on this test or does this seem right. I am going to check the alternator after putting the battery back in. I should get a higher voltage check at the battery if the alternator is working correctly, while the car is running. If the alternator is not working correctly I should get a lower voltage reading. Is this correct. Sorry for the long post and so many questions just want to get this figured out. If every thing checks ok, then onto the ignition switch.

 

You want to check your alternator output with a lead on the big red wire on the back of the alternator and the other lead to the case or ground. Should be 14 to 14.5 volts. If not then you have an alternator problem. The reason to check it there is because that wire doesn't go directly to the battery. It goes to the solenoid on the starter first and then to the battery. If you have good voltage at the alternator and not at the battery then you probably have a loose connection at the starter solenoid. Ask me how I know. If you do have a loose connection at the solenoid make sure you disconnect the battery negative cable before you try to get a wrench on that nut to tighten it up or you will have major problems!

 

I posted my results in the first post on the battery and the alternator testing from yesterday and today. I guess maybe start trouble shooting the ignition switch or getting a battery charger for when it sits.

 

Sounds like it is charging OK unless you have a intermittent connection issue. If you continue to have battery drain then we can give you some guidance.

Here is a schematic that might help if you need to look at the charging system some more.