Email from reader …
The other day we received a question from Nanci, who wrote about a problem with her Keurig overflowing the coffee cup (you can also see the original message in our comments section here):
“My Keurig is not making the right size cup of coffee. I put it on the 8 oz size, and it keeps putting water out to almost 2 cups of water. Cleaned it and put in a new filter still over flows the cup.”.
The problem Nanci faces with her Keurig could be from a couple of different faults. The first cause could be a disturbance to the air pump signals or a problem with the pump itself. You make your cup selection from the top pad of the Keurig. Underneath the cup size selection buttons is the Keurig’s brain – or central processing unit.
The second issue causing the overflowing cup is the cup selection sensors themselves, which sit inside the central boiler unit inside the Keurig. The first photo below shows the sensors that sit on top of the boiler unit and the connection to the water level sensor probes. The Black wire is the small cup (6 oz), the white wire is the medium cup (8 oz), and the red wire connects to the large cup sensor (10 oz). In the second photo, you can see where these three wires end up on the Keurig’s main power board.
Ok, so what are our options for fixing this problem? Set out below are our proposed solutions, starting with the easiest and working down from there. Despite being just large water heaters, Keurig brewers are pretty complex, so finding the solution can take a little time.
Health Warning: if your brewer is still in warranty, do not attempt any repairs. Instead, get hold of Keurig Customer Service. Under their one year warranty, you can have a replacement brewer sent out. Any repairs you attempt yourself will invalidate any warranty you may have left.
Solution One – The Keurig Burp
This is the easiest step to fixing this type of problem, and we have written a short guide to take you through the five-step process (don’t worry, it only takes about a minute). Check out our guide by following this link, or you can go to our main Repair Guide section.
Solution Two – Water Senor Check
Removal of Outer Casing
If solution one hasn’t stopped the cup from overflowing, we can now check the Keurig water sensors. We want to make sure they are connecting correctly. For this solution, you will need to remove the outer casing of your Keurig. And then access the top of the water boiler and the main power board.
This might seem a bit daunting, it was for us first time too, but we can help you through it. If you would like some guidance, first watch our two-part video on getting the casing off your Keurig.
Once you have that done, you need to look at the sensor connections on top of the water boiler. As you saw in the second photo above, there usually are three (although some Keurig’s only have two) wires that connect to the water sensor probes that go into the sealed boiler unit. Make sure these connections are clean with no evidence of arching or buildups.
Power Board Connection
If the sensor connections are clean and seem OK, we now need to check on wires that are still properly attached to the main power board. As you can see from the photo, the board sits on the left of most Keurig’s and will have a plastic casing. Typically only four screws will hold this in place, and it’s not difficult to detach. Be careful in pulling the case off, I just let it swing to the right, and with that, you should be able to see where the three (or two) sensor wires attach to the board.
Ensure the connector is fitted to the board and the wires to the boiler unit are not bent or broken. If the boiler unit connections are OK and the link to the board looks good, the water sensors are unlikely to be the problem.
Solution Three – Micro Processor Board Replacement
Solution three involves replacing the microprocessing board. These units are not expensive, and we find ebay.com the best source of reliable brand new or second-hand boards. In buying a replacement board, you do not need the power board connector, air pressure hose, or board casing. However, it could be helpful to have these parts connected as you then have some backup parts.
If you would like to follow this link over to our Parts Replacement page, you can find a review and a link to a wide variety available on ebay.com.
Once you have purchased your replacement board, you now need to work through the steps required to get it replaced. Our Micro Processor Board Replacement Guide will help you through this.
Don’t be put off; we take you through each step, and you have already done the most challenging stage, and that was removing the Keurig’s outer casing.
Solution Four – Air Pump Replacement
The final solution we have for fixing the overflowing cup problem is replacing the Keurig air pump. So far, we have looked at how the water sensors are connected. And then replacing the board that processors the signals and has the processing code on board. And finally, it’s dealing with the air pump itself.
We have a repair guide for replacing the air pump, and you can work through this guide by following this link. Again as you have the outer casing off already, putting in a new air pump is relatively straightforward.
You can find the pump you will need on our Parts Replacement page, and we find ebay.com the best source for these components.