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This seems like the perfect website to chat about my e46 :) Had it for 6 months and in love! I tried to investigate as much as I can before posting...

I have a 2004 330ci convertible that I stupidly let die over the winter months. It was fully dead (no dash lights or clicking in key position 2). I had CAA boost it today (they connected both + & - to my battery).

It started fine but my stereo and dash were reset. However, no warning lights. I had the stereo, seat warmer & heater running. My convertible up-light was flashing (error position) so I was pushing those buttons to ensure the top was in the proper position. The stereo started turning itself on/off and the car went fully dead again. I thought maybe I overworked the battery.

CAA boosted it a second time. I had it running for 10mins without any power features on and even drove it down my driveway. But as soon as I touched the power window the car instantly died again.

What's going on here? Is it an alternator or battery issue? Or, I wonder if it has something to do the with computer being reset.

Aside from that for my own understanding, was it correct for CAA to connect the negative terminal to my battery? I read negative should connect to the metal frame for grounding and preserve the computer. Was the computer reset simply from not being started for 6 weeks in the sub-zero winter or did CAA screw it up?

Thanks!
 

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This seems like the perfect website to chat about my e46 :) Had it for 6 months and in love! I tried to investigate as much as I can before posting...

I have a 2004 330ci convertible that I stupidly let die over the winter months. It was fully dead (no dash lights or clicking in key position 2). I had CAA boost it today (they connected both + & - to my battery).

It started fine but my stereo and dash were reset. However, no warning lights. I had the stereo, seat warmer & heater running. My convertible up-light was flashing (error position) so I was pushing those buttons to ensure the top was in the proper position. The stereo started turning itself on/off and the car went fully dead again. I thought maybe I overworked the battery.

CAA boosted it a second time. I had it running for 10mins without any power features on and even drove it down my driveway. But as soon as I touched the power window the car instantly died again.

What's going on here? Is it an alternator or battery issue? Or, I wonder if it has something to do the with computer being reset.

Aside from that for my own understanding, was it correct for CAA to connect the negative terminal to my battery? I read negative should connect to the metal frame for grounding and preserve the computer. Was the computer reset simply from not being started for 6 weeks in the sub-zero winter or did CAA screw it up?

Thanks!
With all of this going on.. wouldn't it be wise to just buy a battery and test if that's what the issue is? It's MAYBE $150 from a local shop with your required specs. Hey if that doesn't work, at least you'll have a new battery ;)

Sent from my SAMSUNG-SM-G920A using E46Fanatics mobile app
 

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On the other hand, it kind of sounds like your alternator isn't able to continuously charge the battery! I'm sure there's more experienced E46 members here. But, that's kind of the point of the alternator. The computer is reset every time the battery will go out and you'll have to jump it on or "boost" it. Don't worry too much about that.

Sent from my SAMSUNG-SM-G920A using E46Fanatics mobile app
 

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Before taking anything apart get a multimeter out and read the DC voltage of your battery when the car is off. Should be around 12.6V, 12.3-12.1V is low. Anything lower than that is a real issue. After starting the car read the voltage again, expect 13.5-14.5V with a functional alternator. If you do not get voltage readings in these ranges you have probably a bad battery and/or dead alternator.

Check the voltage regulator if you suspect the alternator after testing. It is mounted on the rear of the alternator, depending on the brand of alternator, Bosch or Valeo, it is about $35. Much cheaper than an entirely new unit if your bearings are still good.
 

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Before taking anything apart get a multimeter out and read the DC voltage of your battery when the car is off. Should be around 12.6V, 12.3-12.1V is low. Anything lower than that is a real issue. After starting the car read the voltage again, expect 13.5-14.5V with a functional alternator. If you do not get voltage readings in these ranges you have probably a bad battery and/or dead alternator.

Check the voltage regulator if you suspect the alternator after testing. It is mounted on the rear of the alternator, depending on the brand of alternator, Bosch or Valeo, it is about $35. Much cheaper than an entirely new unit if your bearings are still good.
I agree but hope it isn't a Valeo alternator, the voltage regulators aren't $35, more like triple that. Also don't buy an aftermarket alternator if you decide to go that route. Bosch or Valeo depending on what's in there now.
 

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I agree but hope it isn't a Valeo alternator, the voltage regulators aren't $35, more like triple that. Also don't buy an aftermarket alternator if you decide to go that route. Bosch or Valeo depending on what's in there now.

Exactly. Valeo alternators are better to replace than to just replace the voltage regulator. Bosch regulators are just $35 and are worth it if the rest of the unit is sound.

If the battery is suspected to be bad after voltage testing. Take it out and get a ride to your local auto parts store. They will charge it and then do a more accurate testing of the battery's condition. If you end up needing one then you already have it there to turn in for the core charge!
 

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It doesn't sound like you charged your battery. Charge it first or buy a new one. I've never had a vehicle run good with a really dead battery and I wouldn't recommend charging it with the vehicle as that might overwork your alternator.
 

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Car batteries go bad easily if you fully discharge them, especially if they sit a long time in that state. Yours is likely bad.

Also, the battery's internal resistance often goes up when it goes bad causing your alternator to work like hell trying to charge it. This can overheat and wear out your alternator.
 

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I would invest in a trickle charger for next winter, or anytime you plan to not drive the car for an extended period of time. Inexpensive and reliable.

Battery is most likely dead. I've had this happen to me after leaving an interior light on in the car, got jumped off but ended up having my alternator go out later in the week. Have it charged at an auto parts store and tested, don't keep jumping the car off.
 
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