[Gotulukn]

Hey 2addicts,

I have a 2014 m235i with 99.4k miles. I need opinions and help! Two days ago, my car wouldn't start in the morning, wont even unlock with the remote. OEM battery dated from 2014 was dead, figured it was its time to go. I'm aware of the registering the battery, but I needed my car for work asap. I bought a O.E. spec AGM battery, installed it, car started normally and drove around the block. 3 hours later, bout to head out to dinner. The car was completely dead. I thought the new battery was crap, went back to pepboys and they gave me another one.

This time I bought a multimeter, 12.7v on new battery. I installed the battery today and I did some research, with people saying it could be a faulty IBS. I unplugged the IBS and felt confident the non-start issue is gone. Well, 3 hours later I go out to just check and start the car, I unlocked it with the remote, all the regular lights work normally and car cranks but no ignition, tried again and things got dinner immediately. Multimeter on the battery now says 10.9v!!!

Video of cranking

Unplugged IBS

So it's not my "intelligent battery sensor," im at 99k miles, maybe it's my waterpump running?? I know these pumps are known to fail... Any advice? Or start pulling fuses?

[Aspen235]

Could be many things, somewhere a circuit is drawing power. For me it was a faulty door handle on an e90.
A shop will have a circuit tester so they can narrow down the source. Otherwise you will have a difficult time.

[Liandri]

^what he said. If you want to prove that the car is drawing too much when asleep, you can run the meter inline with the negative battery terminal and do a draw test. Take the terminal off, use the 10a fused lead positions on the meter, attach one to the battery post with a clamp or even tightly wrapped tape, and the other to the removed vehicle-side terminal. Keep them separated and select the amp function on the meter. When you connect it the amperage the car is using will be going through the meter and displayed on the screen. You will probably have to manually close the trunk lock with a screwdriver to fool the microswitch into thinking the trunk lid is closed, and after 20-45 mins the car should normally be down around 50milliamp. My guess is it will be much higher since you seem to have a short somewhere or a module that's incorrectly staying active

[Gotulukn]

Solved!!!

Hey guys, with my amateur troubleshooting skills, and since I was due anyways, changed out for new waterpump and thermostat( just cause), and no more battery drain issues!

It cost a grand, could of been a miss, but glad it wasn't! Was getting tired of leaving the trunk unlatched, and unhooking my battery wherever I parked 😂.

[overcoil]

Originally Posted by Gotulukn

Solved!!!

Hey guys, with my amateur troubleshooting skills, and since I was due anyways, changed out for new waterpump and thermostat( just cause), and no more battery drain issues!

It cost a grand, could of been a miss, but glad it wasn't! Was getting tired of leaving the trunk unlatched, and unhooking my battery wherever I parked ��.

did you do the work yourself ? not sure how much a water pump is so (labor) ...

[Dylan86]

So a battery drain issue was resolved with replacing the waterpump? Possible that the electronic thermostat was causing the drain in this case? This is strange yet intriguing as I've never heard or seen such a thing..

[cooolone2]

You would have heard the water pump running with the engine off. What made you go there? As Dylan noted, this is an very rare example. And a shot in the dark if you didn't find it by troubleshooting and seeing a draw on the WP circuit, whether from a shorted wire, relay, etc.

Have you tested for any residual draw even though the major drain is gone? AGM's have great tolerance for small draws.

Anyways, thanks for update