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Lars(wi) 
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Joined: 14 Sep 2009
Location: Permian Basin
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 Topic: I this is a long shot……………
Posted: 6 hours 37 minutes ago at 10:44am |
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but, is anyone here familiar with BMW’s? Son has a 2015 335i, when the weather turns cooler(under 50 deg F., the battery drains dead. Several battery swaps over the years, has not solved the issue, numerous trip to the stealership temporarily fixes the issue. Last week when I was at his place it happened again, cool day, jump started the car, did his route for the day, came home, shut it off, couple hours later, battery dead as a door nail. Hooked up the charger, after a few minutes, the electric water pump turned on. I know the electric water pumps on these cars are problematic, has anyone conquered this issue. I know BMW’s are an electrical nightmare. Any help/suggestions, or some tanerite would be greatly appreciated.
Edited by Lars(wi) - 6 hours 35 minutes ago at 10:46am
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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jaybmiller
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Joined: 12 Sep 2009
Location: Greensville,Ont
Points: 24820
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Posted: 5 hours 44 minutes ago at 11:37am |
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no ,but it sounds like 'something' is turning on,draining the battery when <50*F. Maybe a seat heater,windshield heater or some other 'hightech' item ?? I'd put an ammeter between battery and 'the rest of the car' to see how much current is being drawn. Any lights on ( under the hood ?). Newer cars have 'CANbus' ballast resistors and they WILL kill a battery. Maybe the alternator is 'kinda' bad ? If ammeter say power is being used, start pulling fuses, one at a time, to locate WHICH circuit it is. Please report back with any new information !
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor)
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AC7060IL
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Joined: 19 Aug 2012
Location: central IL
Points: 3592
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Posted: 5 hours 18 minutes ago at 12:03pm |
Not familiar with particular model. Google it? Search yr model issues & watch internet light up about issues. Good luck. Below is a link of my find from ; “2015 335i battery issues” search Could be it has “on demand” alternator charging?? If so, it’s battery’s ground terminal sensor may be defective? A temp fix ~ delete that sensor for a direct ground. That will produce a constant charge alternator to assist the moment. Get new sensor for long term fix. https://www.reddit.com/r/BmwTech/comments/11x4enb/2015_bmw_335i_battery_discharging_while_stopped_i/
Edited by AC7060IL - 5 hours 2 minutes ago at 12:19pm
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Lars(wi)
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Joined: 14 Sep 2009
Location: Permian Basin
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Posted: 3 hours 43 minutes ago at 1:38pm |
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We have noticed the electric water pump will continue to run after turning off the engine, even after the engine cools. Internet has posted different solutions, we put a new battery a hour ago. Water pump turned on. Some solutions include; unhook battery for several hours to allow ECU to reset, the water pump is faulty ECU is sending signal to w. p. to stay from faulty reading from temp sensor
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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jaybmiller
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Joined: 12 Sep 2009
Location: Greensville,Ont
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Posted: 1 hour 50 minutes ago at 3:31pm |
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OK, I understand why an electric fan to cool the rad down makes sense BUT keeping the waterpump on ?? Query... any idea how LONG the pump runs ? If more than say 5 minutes there HAS to be a problem !
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor)
Never burn your bridges, unless you can walk on water
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Lars(wi)
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Joined: 14 Sep 2009
Location: Permian Basin
Points: 8205
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Posted: 1 hour 1 minutes ago at 4:20pm |
 jaybmiller wrote:
OK, I understand why an electric fan to cool the rad down makes sense BUT keeping the waterpump on ?? Query... any idea how LONG the pump runs ? If more than say 5 minutes there HAS to be a problem ! |
Sometimes the pump will continue, until the battery is dead. Sometimes it shuts off right away. The dead battery issue happens every autumn, and will be an on-again, off-again challenge until spring warm-up.
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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Hubert (Ga)engine7
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Joined: 12 Sep 2009
Location: Jackson Cnty,GA
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Posted: 34 minutes ago at 4:47pm |
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Since it happens during the cooler months I would suspect either a faulty temperature sensor or a faulty ecu. For some reason the ecu senses that there’s too much difference between ambient temperature and engine temperature so it tells the water pump to run. After resetting the ecu it may take a while for it to sense the “problem” again. Wish you luck on finding where the gremlin is hiding.
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Just an old country boy saved by the grace of God.
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