My Keurig only puts out a little more than 1/2 a cup of coffee.
The email from Patten today sounds like an air pump failure on their K40 brewer. The purpose of the air pump is to provide the necessary air pressure to move the heated water from the brewer’s boiler unit and push this through the K Cup holder and then to the coffee cup.
A failing air pump can lead to insufficient air pressure being generated and hence not having enough push to put the correct amount of water into the K Cup and therefore not enough coffee in to the cup.
Air pumps can fail for variety of reasons; these include just general wear and tear and corrosion from leakage of other components inside the brewer (as you can see from the photo below the air pump is right next to the solenoid unit which deals with water pressure).
As we mentioned in our response to Dave back in April, our thinking on this issue is perhaps the problem is being caused by the use of vinegar in the descaling process. Vinegar is what Keurig themselves recommend for use in their machines. But as we looked into this and the rate of failure in pumps and solenoids in their machines we wonder if a significant cause of these types of problems is coming from vinegar usage.
At home we no longer use vinegar in the cleaning of any of our single serve coffee machines but rather use a product marketed by Bosch. This product has been very good and something we now recommend to other Keurig users (this product is also listed on our spare parts page).
However, getting back to the issue for Patten. We have guidance material that addresses this specific problem and provides a number of solutions, including the Keurig Burp and an air pump replacement.