Q: My Electric water pump on my 2014 320i BMW runs constantly after shutdown. Drains the battery dead after about five hours. What

asked by on March 13, 2017

My Electric water pump on my 2014 320i BMW runs constantly after shutdown. Drains the battery dead after about five hours. What controls the water pump's on/off. I can temporarily shut the pump of by locking/unlocking the vehicle 30 seconds later the pump turns on again.

My car has 45000 miles.
My car has an automatic transmission.

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The electric water pump circuit uses both a temperature sensor and a relay to control it’s function. The temperature sensor tells the water pump there is a demand for it to circulate coolant based on engine temperature. The relay acts as the on/off switch to send power to the pump. Either of these can be at fault. The sensor may not be registering temperature correctly so it is constantly calling for the pump to run. The relay can be stuck in the On position as well, never turning power to the pump off. The pump itself can also have an internal short that is causing it to never turn off. Judging by the age and mileage of the vehicle, you may still be under warranty. The BMW factory warranty is 4 years or 50,000 miles, whichever comes first. That applies to any owner and starts from the original sale date of the vehicle. If the vehicle is not longer under warranty, have one of our mobile techs come to you. They can inspect the electric water pump circuit and find the exact cause.

Hi there. The auxiliary water pump is an electronic component, which, unlike the primary water pump that is activated by the drive belt, uses an electric motor to pump coolant. Due to this fact, an electrical short anywhere in the power supply to the pump will not allow the circuit to complete; and cause the pump to stay on at all times. Most of the time, the problem is in the ignition system, the relay or a ground wire that has been damaged somehow. On the BMW, it’s hard wired into the ignition system and not powered by an ancillary fuse. Due to this unfortunately reality, it’s best to have a professional BMW certified mechanic to complete an electrical problems inspection to resolve this annoying problem.

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