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Electric Water Heater current drain

11175 Views 9 Replies 9 Participants Last post by  Bali
Absolutely incredible ... Electric Water Heater working all the time very good but consumes electricity from the battery when the car is turned off. If I don't drive the car two or three days all the power from the battery are empty?! Battery is new and I take my bmw to Electric handyman for cars and he detect that when Electric Water Heater is plug off car don't consume the power from the battery?!
Does anyone now how to resolve my problem (changing the whole part is too expensive)? Can I change the wires from Electric Water Heater?

part number on module: 64126918806
realoem.com shows 64129145439 (supercedes 64126918806)


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Add a switch inline somewhere.

But, this is the first we've heard of such a thing here. Where is this heater? In your hvac box instead of the heater core...or is this the heater core and it just has some electric control unit that's drawing power?

You have a complete PN for it. The one you gave is too short.

Realoem.com might help too. That appears to just be a heater core and it would be heated from hot coolant, not from an electric heating grid, if that's what you think. Ah...there's a temp sensor on it, I believe. Sadly, I think the cost of getting to it through the dash would be high...though I wonder if that sensor might be accessible. I bet that's it...a temp sensor...

or...another theory. You got a new battery and maybe have a failing alt, loose/corroded cables, or you don't take long enough drives to ever get the battery charged fully. You might take lots of short trips and the battery is just weak. You have the volts but not the amps...and it's running low in 3 days. If you have a charger, charge it overnight.

Run the cluster test for voltage and see what Volts you're getting with car off and on...might be just a coincidence...and your mechanic might be picking up just the natural drain the car has while it sits and does nothing.

Finally, another theory would be you got a new heater core because you didn't have heat...and your old heater core was fine but your fan wasn't working because the fsr was broken...and it will drain a battery...very common issue.

...a few theories for you...does your mechanic seem reasonably intelligent?
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Thank you for your answer ... I will try to explain everything.

1. BMW e46 320D year of production 2004.
2. I write this code: NE512P 64.12-6918806
3. Battery charged fully 3. times and I take battery to servis and they told (after they test it) that battery is ok.
4. Electric car servis in one of the best in my town and I took my car to that servis and need all day to find out what component drain out my battery. In the end they found out (when they switch off electric water heater / picture in attach) that electric water heater make that problem. But electric water heater work just fine,only that he drain out every time my battery when car is not driving for two days.
5. Can I somehow put new wiring to the battery or I can put some switch relay that will turn on when I put ignition key?


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Yes, you can add extra circuit to it to control the electric water heater through an ignition switch, but first, is that EWH original equipped with car or someone add it on latter?

If it's original equipped, then you should find out what causes the battery drains and fix the problem rather than try to add some circuit to it.

If it was add on latter, perhaps you or have someone knowledgeable about electrical trace the wiring and should be able to figure it out.
Add a switch or a cutoff inline to its ground, that should kill it when you want to.
Could you clarify what an "electric water heater" is? I have been involved with cars for 50 years and NEVER heard of such a feature on an automobile with an internal combustion engine.
This is a coolant pre-heater - it works in conjunction with the electric water pump so you have heat in the winter sooner and the engine warms up quicker. It should be only working while the coolant temperature is in the blue area and then should turn off. If it drains the battery, means the control module part of it is shorted/dead. Replace it or unplug it - it is not vital for car operation, only for the comfort to some extend.
I have experienced the same problem as Nesmajnik with my BMW 330 Cd, the battery weakens in few days when the car is not used, and then it cannot turn the engine (diesel) fast enough to start. Using a DC current clamp meter (with Hall sensor) I have found all time the 0.3A leakage current goes through this EWH. The EWH heater is factory connected to battery thick red cable which comes from the battery to of starter solenoid. This circuit is ready for high current. Possibly there is a relay inside EWH which switches on/off the heater, but this relay is bridged by some dirt or carbon deposit which results in leakage. Does anyone know what is inside the EWH?
Does anyone know what is inside the EWH?
Open it up and have a look.
I would get a good used replacement, code it to my car, and be done.
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