Blinking Blue Light on B40

Photo of the blue that sits at the bottom of the water reservoir cradle




April 20, 2013


The blue light was blinking, I added water – it is still blinking and will not brew coffee. I’ve turned off the machine, waited and turned back on, still blinking to add water and it is full of water. What should I do?


On a Keurig B40 brewer the blue light refers to the ADD WATER function. And when its flashing it means the machine thinks there is no water in reservoir and so is requesting the user to add some in. Of course what is a common problem, as Sam is experiencing in this case, there is in fact plenty of water in the reservoir but the signal between that and the brewer’s processor is being blocked or breaking down in some way.

So let’s look at a B40’s normal operation and how this situation can arise.When the power switch is pressed a signal is sent to the water pump to get ready and through the movement on water within the internal plumbing water pressure will cause a pressure change to bring water out of the water reservoir and in to the boiler or heater unit (its the large cylinder in side the machine that holds the heating elements). Inside the boiler the water will rise to the point relating to the cup size selected, as measured by a probe inside.

So the break down we have in Sam’s case is most likely to do with a problem with the water sensors, of which two parts we need to check. The first is straight forward enough and that is taking the water reservoir and checking that the magnetic disk on the inside of the reservoir moves up and down freely. As you can see from the photo below the disk needs to be able to travel up and down its enclosure without impediment.

B60 Magnetic Water Sensor


If this disk appears to be working ok the next step is more complex and involves checking on the fixed magnetic sensor inside the machine itself. The photo below shows the senor on our B60, where its attached to the left side wall (looking straight onto the machine). We have removed the two screws the attach it to the side wall just so it stands out a bit more in the photo. This sensor is then connected up into the circuit board of the brewer (which sites on the opposite side of the machine). Being able to check on this sensor and making sure its wires are not broken or the connection has become loose involves removing the Keurig’s outer casing. For more information about this check out our maintenance video section and the two videos we have to help fix this problem. If the sensor does require replacement we have included this component on a Replacement Parts page if you wish to purchase online.

B60 Magnetic Sensor