I have no idea why my car will drain a good battery down. Car will start cold. drive it around for a while. when I go to restart the car it will draw the battery down. when I get it to start it will run for a few minutes then slowly die when going down the road.(I was stuck on the side of road until I could get a jump start)  I have been told wiring harness?  bad ignition? coil?  The car is no good if it is not somewhat reliable. No fun with a nice looking 1969 red corvette 427 that you cannot enjoy.  Any suggestions?  Thanks

Bad battery
Bad alternator

That's where I would start.  Get it.....start?

Definately check the alternator,  get a voltmeter(don't solely rely on the dash meter) and check the voltage at the battery before starting(if well charged it will read around 12.6 volts) and then start engine, and recheck the voltage at the battery again, it should be higher than the previous reading, somewhere in the 13 volt range, maybe just at 14.... if not, idle up the engine around 1000-1200 and check the voltage, if still nothing then its probably the alternator....    typically the alternator will keep the engine running regardless of the battery, but not all alternators will work without a battery energizing the alternator, most 'older' alternators will, newer ones not so much...)  


|UPDATED|7/22/2017 5:52:25 PM (AZT)|/UPDATED|

Most auto parts stores will test both your alternator and your battery for free.

Thanks for the info. The alternator was checked and it is putting out the correct voltage. The alternator was just overhauled a couple of months ago.Battery is a red top optima and it is new.  Now on to checking the cables.

well, i would still test the alternator, just for peace of mind... even just being rebuilt, 'things' happen....   and being an Optima battery, they do fail too...especially since Johnson Control bought out Optima and quality kinda suffered...  

Optimas are definitely not what they used to be.

Has the voltage been checked AT the battery while running? Doesn't matter how the alternator works off the car if it doesn't get the voltage back to the battery. Assuming your '69 still has the separate voltage regulator on it, I would start with that. A bad/loose connection anywhere in the system will fail more when hot than cold. Dying while driving points to a loss of voltage due to no alternator input....whether it's because of a loose connection, or failing alternator output, or faulty voltage regulator. Other thing could also cause it to die like that, but your particular combination of no start when hot, having to jump it off, and it dying while driving points to a loss of voltage issue.
Put a voltmeter on the battery and see if the voltage takes a dive while driving. If it does, check the voltage at the alternator at the same time.
Check all of the battery cable connections on BOTH ends. Battery ground is under the driver seat, connected to the frame. The engine ground cable comes from the passenger side frame over to the engine block, usually right around the starter/engine mount.

Thanks. I had the alternator checked while on the car and running. It is producing the correct volts. The battery is new and it was checked at local auto store.  The starter is a new mini type. factory manifolds .  I can check the cables and grounds.

Another way to rule out the alternator is to disconnect the battery with the car running. If the car dies then it's the alternator because once a car has been started and is running, the alternator should carry it without the battery.