Before I get into the how-to part, I'd like to explain a bit of background about this coffee machine and it's problem.
I purchased the unit as-is on ebay with the intention of fixing it, however I found it too difficult and time consuming to take apart and set it aside in favor of repairing other things. Just about a week ago, I dug it out of my basement, and got to work on it.
The Problem The machine will take water from the basin, the valves work, but it does not brew a full cup of coffee. This seems to be a common failure with this unit.
The Cause Water is being fed into the air pump located at the bottom of the unit causing it to rust and seize. In this tutorial, I will explain how to disassemble your machine and fix this issue.
On to the disassembly...
You will need to flip your unit on its side for the repair procedure. Lay cloths or paper towels underneath the unit, as it will leak from the K-CUP arm.
- Remove the bottom plate. There are a few Philips screws holding the metal plate on. The grounding wires are riveted onto the metal plate, preventing complete removal of the plate.
- You are now ready to remove the plastic frame. Locate the screws for this frame around the bottom edge of the unit. There is another screw by the drip tray, and another by the basin pump. Do not pull the frame yet.
- The basin pump and basin LEDs must be removed now. Locate the 1 screw for the LED and the 2 screws for the mouth of the basin pump. These are located directly below the basin.
- Pull the frame out and de-route the power cable (optional). Be careful of the basin pump, you will need to bend the tube connecting it to the pump. You may want to unscrew the pump.
- Remove the 2 screws from the underside of the K-CUP arm. Open the K-CUP arm. Remove the holder.
- Remove the 2 black screws located in front of the holder (inside bottom). The body piece will fall off, hold it up with your hand when unscrewing then pull it off.
- Look directly above of those 2 black screws, you should see two more screws on the top of the K-CUP arm. Remove those screws and slide the body piece out from underneath the handle.
- Remove the 2 screws securing the top cover to the frame of the unit. These are higher than the K-CUP arm's two screws. You only need to remove the top cover's two screws. Pull the top cover up from the gap, this will not remove it but it will loosen the clips for removal.
- Flip the unit on its side again.
- Get a flash light and look in the cavity where the water basin was, locate the clip securing the top cover of the unit to the case. It is located directly back of where you are looking, it is not on the side wall of the unit. Pry it back towards the back of the unit and push up. This requires a lot of force, you may want to use a long screwdriver or tiny crowbar.
- Stand the unit up again.
- While the unit is still on its side, pull up the top cover a bit more. Shine a flash light into the gap and locate another clip on the back side of the unit. Use a screwdriver to push and pry upwards on the clip. It should come loose. Do this for the next few clips as the come loose. Pull off the top cover.
- Unscrew the two screws above the LCD. Unscrew the screw securing the back cover to the front panel on the other side of the unit. Slide the back cover down and pull it back to remove.
- Your brewer is now fully disassembled. If i missed a step, please correct me, but i think everything is correct.
You can now replace the 2 valves in the unit, repair any leaks, repair electrical connections (the power board is located on the LCD side of the unit near the bottom in a black box.), repair non-functional pumps, and re-prime your brewer.
However, I will go over how I repaired the problem with the brewer not pumping water.
The pump is located at the bottom of the unit, on the side opposite of the LCD. Remove the pump by unscrewing the unit and desoldering the connections (underneath black heatshrink tubes). Make note of the polarity before removing.
Remove the tube from the pump, if there is water in it you will need to drain the tube and then flush the unit's tubing. We will do this after re-installing the the pump.
Pull the tube out, and remove the three black screws from the pump. Remove the white plastic cover. You do not need to remove anything else on the pump.
Rinse your tube under a faucet, making sure to get water into the holes on top of the pump. Shake the pump vigorously to remove the residue causing the motor to seize.
Test the pump by plugging it into a 12V power supply. I cut an old phone power supply and attached the wires to the leads of the motor. Polarity does not matter while testing.
Repeat the rinse and shake process if the motor sounds like it is slowing down every so often. It should be running quickly at a constant speed.
Once it passes testing, dip the pump in cleaning alcohol then shake out the excess. This will speed up the drying process. You may want to wait a while before reinstalling, but it usually does not matter since cleaning alcohol will not conduct electricity.
Resolder the wires, use heatshrink tubing or electrical tape around the connections. Reinstall the pump into the unit and attach the tube, using a zip-tie to secure it. You may want to re-prime your machine before preforming a test brew.
Remove the tube running from the water reservoir to the K-CUP arm unplug it from the percolator only, leave it attached to the reservoir.
Remove the large tube that runs from the underside of the reservoir (the bottom is metal), unplug it from the black tube splitter only! Do not unplug it from the bottom, unless of course you'd like to spend the rest of the day mopping up water. This is where the water will come out when we empty the reservoir, place a cup at the end of the tube so it will drain into it.
Blow air through the tube that lead to the K-CUP arm. I just used my mouth, but if you're a clean-freak you may want to complicate the process by using a pump.
Once the reservoir is empty, plug the tubes back in. You do not need to use a zip-tie until reassembly.
Flip the unit on its side and reinstall the frame. Reroute and screw in the water basin pump mouth. Flip the unit back over and install the water basin.
Entering prime mode
With an empty reservoir, turn the machine on and wait for it to say "Ready to brew"
Press brew and wait 60 seconds. Attempt to turn the machine off with the switch. If it does not turn off, you are now able to enter prime mode. If it turns off, repeat the first step and wait longer.
Unplug your machine, keep the cord near the power socket and hold it with one hand. Press Left + Menu + Right and plug the machine in. The LCD should stay off, or flash blue and then turn off. Press brew in addition to the other keys. Keep holding these down for the next step.
Reach around the unit with your hand still on the buttons and press the on/off switch on the back of the unit. The unit should automatically start filling the reservoir and then start brewing a cup of coffee. If it does not start, press brew immediately after the screen comes on.
Perform a test brew and reassemble the unit.
Congratulations, you've fixed your pump and successfully repaired your keurig B70!
More pointers for the mechanically inclined:
- EmmJayEff's theory of operation and tube routing diagram [.pdf, updated 7/21/12]
- Jay Aitchsee's simplified operational diagram
- EmmJayEff's schematic and parts list for the solenoid/air pump/water pump driver circuits on the KE779L7 power board [.pdf, updated 9/29/11]