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Mercedes Benz W210 E200 CDI
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Discussion Starter #1
Hello all,

I have a strange motor running all the time and draining my battery. Battery goes empty after about three weeks of using the car. We have checked all the fuses one by one and found that number 4 (ADS SE) if faulty and causing the battery drain. After that we have also found that some strange motor is running full time under the hood. What is motor for? It looks like it is pumping some fluid around the car.
What control box is responsible for this unit?
Thank you!
 

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2001 SLK 320(217K Miles), 2002 E320 Special Edition(183K Miles)
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3,467 Posts
That is the coolant recirculation pump. It is suppose to run whenever the car is switched on (key in position 2 or engine running) or if the recirc button on the AC controls is pressed.
Its function is to ensure an even hot water flow into the cabin heater. You do not mention from which country you are, but based on the engine size and the rust inside the engine compartment, I think you probably need the heat in the cabin.
 

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E320/E250 Bluetec Ford F350 6.7l
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36,720 Posts
That pump still should go off with ignition off, although some models have it running few minutes after engine shut down to prevent hot spots on the engine.
The small draw should not drain battery when you drive the car everyday. So is it 3 weeks of parking that kills the battery?
 

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Mercedes Benz W210 E200 CDI
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Discussion Starter #4
I turned the pump off because of battery drain. It is working 24/7 and draining my battery. But I think it should go off sometimes? I have 0,78A drain because of it, all the time.
Im living in Finland. So yes I need heater =)) sometimes when it goes below -25C.
Im also using my car daily, driving for about 50 km a day but then it stays on the parking lot at the night and this motor keeps running all the time. I charge battery to the full and Im able to use it for about 3 weeks and then it slowly goes empty so Im not able to start my car one morning.
 

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E320/E250 Bluetec Ford F350 6.7l
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36,720 Posts
Disconnecting the pump can be emergency fix, but beside having less heating, the operating circuit is has to stay on all the time, so small draw will be still present.
Is your car going to sleep after about a minute since you get out? All lights and displays off?
 

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Mercedes Benz W210 E200 CDI
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Discussion Starter #6
Hi, I have tried to connect the pump again while the ignition was off and it still working after a night standing in the parking lot. So once I connect the plug it turns on. REST button on the dash is turned off.
There is also some kind of relay on the connector to the motor. Is it home made or should there be one?

I will post the video soon about this problem.

Thank you!
 

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Mercedes Benz W210 E200 CDI
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Discussion Starter #8
I have changed the relay (12V/30A) and it seems working. When I press REST or turn the ignition ON pump starts going. When ignition is OFF pump stays OFF as well.
However don't know why this relay is there and where the wires go.
I have been the owner of this car for about a 1/2 year and problem appeared couple of months ago.
 
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