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How to Repair a Bunn Coffee Maker

Bunn coffee makers are known for their quality, but they still sometimes need repairs. Here is some step-by-step guidance for some of the most common problems:

For each repair, first unplug the coffee maker and empty the water.

  1. Water isn’t hot. The main heating coil may have failed. Remove the outer cover. (Depending on the model, there may be two screws underneath the filler reservoir lid and four on the outer cover.) Then remove the pan to reveal the water tank and heating assembly. Some problems will be visible, such as a burst heating coil. Other times, you’ll need a multimeter to test whether electricity will run through the main heating coil. If it does, the multimeter will beep. If the problem remains, check the limit thermostat, control board, thermal fuses, tank heater switch, and probes.
  2. Heating pans don’t heat. A thermal fuse may be blown. Remove the outer cover and inner panel to reveal sleeved, V-shaped fuses. Slide them out of their brackets. Cut the wires at the old crimp and strip the wires about ¼ inch. Crimp the new fuses in place, replace the fuse sleeves, and slide the fuses into their brackets. Reassemble the coffee maker. Before turning it on, fill the machine completely with water, holding down the (white) fill flow lever to fill the inner reservoir until water comes out the basket. Then, release the lever and fill the upper tank. Turn on the coffee maker and wait for the water to heat.
  3. The coffee maker leaks. This typically signals that a seal is broken, allowing water into the casing. Remove the top outer cover, and then the top cap and the plunger. This will expose two more Philips screws. Underneath the plunger, remove the nut keeping both a metal washer and rubber gasket in place. Often the leak is caused by breaks to either of these two parts. Replacing them should solve the problem. (Some repair specialists say installing a larger rubber gasket or covering the damaged gasket or washer with silicone is effective when OEM parts aren’t available. Another says a faucet seating kit from Price Pfister is an effective replacement.)
  4. Water overflows. Check the unit for a clogged or broken spray head. Remove the drawer where the coffee grounds are placed. Unscrew the seal and spray head. Use a deliming tool or toothpick to remove mineral deposits on the spray head holes. Clean deposits from the inside of the tube with the handle of the deliming tool or with a deliming spring. Clean with detergent and a soft cloth, and rinse. If the seal and spray head became separated, reseat them, paying attention to identify the tops of both pieces. Insert the spray head into the seal and screw the unit into the coffeemaker. Also, ensure the machine is set to the correct brew volume.

Some issues may not require repairs. For example, overflows may be caused by using a broken grounds basket or one not designed for this unit, by an improper grind, or even by using a different filter paper. Use the brand recommended by the manufacturer.

In all cases, clean the unit. Lime scale and mineral deposits can cause a host of problems from spitting water and excessive steam generation to weak brews and vibrations. De-liming and thoroughly cleaning the unit inside helps resolve problems and minimize future repairs. (Be sure to remove all cleaning solutions by running three cycles of water through the machine afterwards.)

For more tips, check PartsTown’s blog on Bunn.