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View Full Version : Weird Electrical Problem / Drainage


njshore4x4
06-21-2006, 06:15 AM
OK, here goes. Went to start my car and it started but acted like battery was weak. The battery is less than 3 months old so I was concerned. I drove the car for over 2 hours before I shut it off for about 5 minutes as I ran in the store. When I came out, the car wouldn't start under the power of the battery but did with a jump. With a jump, the starter seemed to turn over at normal speed and car started right up. I took off the negative cable to the battery and the car stayed running so the alternator is working. I have not checked with a voltmeter what is coming back to the battery and the actual battery voltage.

So, what should the voltage back to the battery be, I guess around 12-14 volts, can anyone confirm this?

Can anyone suggest points of power drainage? I noticed that my sunroof, you have to click the switch a few times in order for the roof to close. This was never the case before this happened. There are some fuses and relays adjacent to the battery under the rear seat. One relay I can hear is the sunroof relay. Whats the rest?

This power drainage was intermittent but seems way more frequent lately. Every morning the car will start but acts like battery is weak.
Ausmpower
06-21-2006, 06:26 AM
Voltage should be around 13.8- 14.4 volts.

With your mileage your probably due for a new regulator and brushes.
njshore4x4
06-21-2006, 02:04 PM
A bad regulator would eventually drain the battery dead and the low voltage would cause the car to run funny and eventually die completely. It started funny this morning and I was able to drive 60 miles to work. Then leaving work it started again like it had a weak battery and I drove 60 miles home. Also if the regulator was bad, when I disconnected the negative battery cable, the car would just die or start spurting but it stayed running. I wonder if my starter is starting to go bad. I really need to get to my shop to get my multimeter!!!!
laguner
06-21-2006, 03:38 PM
If the battery has a charge, the car will run without a perfect alternator for a while. Check voltage at battery when running. If discharging....Starter does not sound like an issue if the car starts with a jump.
njshore4x4
06-23-2006, 05:37 AM
HERES THE LATEST.

voltmeter doesn't lie.

Car off, battery voltage = 9V
Crank a few times, no start, battery voltage = 3-5 V
Car running at idle voltmeter = 13.6-13.9 V

conclusion = dead battery.

Thanks everyone for some good ideas!! ron
Qube
06-23-2006, 06:07 AM
I'd believe you can check with your OBC as well, the running voltage among other things :)
njshore4x4
06-23-2006, 09:16 AM
how do you use the OBC?
Qube
06-23-2006, 09:21 AM
how do you use the OBC?

http://www.m5board.com/vbulletin/showthread.php?t=6767

Cheers
joshua43214
06-24-2006, 04:22 AM
Never, ever, remove the battery terminals from a car with a alternator. This is an old world thing from when cars still had generators. You can very easily blow the diodes in an alternator if the batery is not in the circuit.
Ausmpower
06-24-2006, 09:49 PM
Never, ever, remove the battery terminals from a car with a alternator. This is an old world thing from when cars still had generators. You can very easily blow the diodes in an alternator if the batery is not in the circuit.

Not to mention voltage spiking and frying any number of critical modules....
joshua43214
06-25-2006, 07:59 AM
Not to mention voltage spiking and frying any number of critical modules....

Ya, thanks I forgot to mention that, lets include never jump start an e34 or jump another car with it. If you aboslutley must jump, turn on the high beams, fan to max, AC on, rear defrost. Basicaly turn on every thing that draws alot of power, then disconnect the cables.