My battery is intermittantly being drained. My car will start, with trouble, most of the time and will run without problems, again most of the time. But several times now my car has died while my wife was driving it and she was unable to restart due to a drained battery. Im wondering what would cause this.

Instrument cluster ,maybe . Watch part 1 an part 2 , silver migration problem ,google that .
Chevrolet Truck Battery Dies Overnight Part

Car will sometimes not start after warm. - CarGurus

www.cargurus.com > Questions > Pontiac > Grand Prix

CarGurusJan 2, 2013 - When i start my car, for the first time during the day- I have no problem.... When I go somewhere and shut it off, sometimes it won't resatrt. ... I have to keep my foot on the gas and rev it up to keep it running- then it's fine. .... When your carstarts fine cold, then fails to restart while warm, it is usually a coolant ...

Blazer has to be jumped, then i shut it off and won't start.

www.cargurus.com > Questions > Chevrolet > Blazer

CarGurusDec 21, 2013 - I jumped it and it ran fine, but as soon as I turned it off I couldn't start it again. No clicking just like the battery is drained. ... Then run the car for ten minutes and shut it off and if does not start, replace the battery. ... Blazer starts fine first time but after shutting off,has hard time starting-takes up to 10 key turns or ...

Engine Performance Problems Due to Crankshaft Position ...

repairpal.com > Problems > Mercedes-Benz > ML320

"Crank no Start" Due to Failed Crankshaft Position Sensor on Mercedes-Benz ML320... It usually ocurs after I've turned the car off and try to restart after about 15 minutes. I typically allow it to ... fine. Stalling and starting problems intermittent at first, but now more frequent. ... Car runs fine then without out warning it won't start.

Intermittent problem= install a temp test light to last glow plug, when doesnt start see if test light is on for about 10 seconds

try starting the car and while running disconnect the negative battery cable,if the car still runs turn on the head lights,if the car dies the alternator is weak. I think its weak and can charge the battery as long as the lights are off,but cant keep up when theyare on. so if drive most of the time in the day time you are ok as long as you dont have to start the car too many times. when you drive with the lights on and the engine slows to an idle like when you park the car dies. make sense?

drive belt tension
have the voltage regulator checked /replaced
if it is faulty the battery will drain as it is running all of the electronics without help from a alternator
AS the ecm draws a lot of current, a battery not charging will not last long
most modern cars run about 85% of the alternator with the rest for charging the battery
if the voltage regulator is part of the ECM, replace the ecm unit

How old is the battery, and what is the battery voltage without the engine running and with the engine running?

First, have the new battery tested & fully recharged.

You may find you problem at any point along the way but here is the proper procedure.

Now, you will need a digital voltmeter to really perform this test properly and be prepared to have a blown fuse or two, as you will be testing the system by removing and replacing them.

Install the freshly charged battery, making sure the terminals are clean and well protected with vaseline or grease. Install the Neg (-) connection last when installing the battery, remove it first when taking the batt. out. Check your negative connections.

Before connecting the Neg. cable, take a reading with the voltmeter to see what the current voltage is, it should remain fairly constant with a good strong battery when disconnected well over 12.6 volts.

Connect the Neg cable and connect the multimeter again, you should now see it start to drop, depending on what is draining the battery, fast or slow. If you note this drain is heavy, remove the neg cable again.

Make sure all things are turned off, brake lights are off when pedal isn't being pushed, no interior or trunk lights left on.

Next, start the car, the multimeter voltage reading should increase or hold steady, no drain or the alternator is not charging and could actually be draining the battery. Check belts and wiring harness plug-in.

If you haven't found your problem, make note of the fuse positions and remove them all. Connect the battery Neg cable and test for drain again. If the car isn't draining anymore, install a fuse at a time until you find the one causing the drain of voltage & then you'll have to trouble shoot that system.

There is a tool that fits over the wiring that will indicate current usage without removing the fuses and such, it's available at most parts stores but until you have one this is the way to find the problem. Isolate it.

good luck

if it clicks when your trying to start it then its the battery i had the same problem

You have all the symptoms of a low voltage condition in the battery, Kragen and other parts stores like it will test your battery and charging system (alternator) for free, but it is pretty safe to say the battery is toast. Don't reject this solution without the test being done, I think you will find I am right, low battery voltage can cause trouble codes to be set and low fuel pressure to name a few..

Sounds like an alternator problem. A bad diode can drain the battery(feed back). Replace alternator and if battery is more than 3 years old replace it too. It takes 20 amps just to power the fuel injection. The Bosch alternator should be rated at 100 amps or better. Low output will affect everything you described. Perform an OBDII scan for a look at stored faults. Let the scan be a guide to any other problems that may be present