charging system issue

[straight6pwr]

background:

i'm driving around one night and the car dies (obviously lost electricity: radio killed first, then dash lights, then car started sputtering.) get the car jumped and had enough juice to get it home before it died again.

so i check service records and the battery is 7.5 y/o so i figure it could be that and it could use a new battery anyhow. got a new battery and threw it in. the car ran for about 25 mins and died again.

so now i think it must be the alternator. rip that out. the brushes on the voltage regulator are worn below spec and the bearing is pretty bad so i go ahead and buy a rebuilt bosch unit. car starts right up from a dead battery and runs for 10 mins no problem. so of course i think problem solved. i find out thats not true and i take it to run errands. on the way back the car dies again. got it jumped and back home and thats where i am now.

anyone know what the hell is wrong? i know everything is installed right i triple checked. thanks.

[AndrewBird]

A very dead battery will kill a new alternator pretty quick. You should always charge a dead battery with a battery charger before driving the car.

If the alternator didn't die, I would assume you have a short somewhere, grounding something out and causing the battery to drain. With everything turned off, unhook the negative battery cable and then touch it to the negative battery terminal. If there is a spark, there is some kind of load on the battery. Don't worry about the OBC or ECU drawing power, as they wouldn't draw enough power to cause a spark.

If it does spark, then you have a short somewhere. Starting pulling fuses one at a time and re-test the battery cable. When you get no spark, the fuse you pulled is the circuit that is grounding out. Next would be to trace all the wires on that circuit and see what the problem is.

[straight6pwr]

yes there is a spark and it turns out to be fuse #21.

21 - 7.5 - Glovebox light
Flashlight
Ignition Key/Seat Belt warning
Interior Lights
Radio Memory
Trunk Light
Active Check Control
Service Interval Indicator
OBC
Fuel delivery
Tachometer/Fuel Economy Gauge
Digital Clock
Multi Function Clock

now i have no experience with electronics so should i bring my car to a shop or is this something i can find myself? i have a manual with diagrams here but its like a foreign language to me

[Mike325]

Some of thoes things you could test by seeing if they stay on when they shouldn't.

[straight6pwr]

Some of thoes things you could test by seeing if they stay on when they shouldn't.

none of those things stay on when the car is off.

[Mike325]

Ya, but maybe your glove box light is staying on all the time or something like that.

[bmwcr89]

none of those things stay on when the car is off.

Have you fix this problem???

[matrix]

How do you know if your glove box is still on?

[AndrewBird]

Holy thread bump!

You mean the light in the glove box? You should be able to see a glow coming from the glove box in the dark maybe. Either that, or unhook the bulb holder and let it hang below the box so you can see it after you close the glove box.