Tag Archives: Coffee

Coffeemaker not Brewing

Electrical/Electronic, repair and reuse, , , , ,

Our Black and Decker coffeemaker stopped working. The clock was fine. When we pressed the ON button, there was the usual “click” sound, but the coffee simply didn’t brew. Nothing got hot. Okay, let’s open it up to see what’s wrong.

Underneath, there were 4 security screws and one plain Phillips head screw. For some reason, small appliances love to use security screws. Why?? This type had a bump in the middle of the slot, to prevent an ordinary Yankee screwdriver from fitting. The lone Phillips screw adds insult to injury. Instead of using a single tool to disassemble this beast, I have to switch screwdrivers.
I got the crappiest screwdriver from a flea market, and ground a slot into the tip with a rotary tool. This technique works for other security screws, too. For instance, if the screw has a triangle head, I could grind a junk screwdriver to fit.
The tool worked. This is what the screw looks like, if anyone is interested.
Even after all the screws are removed, the bottom of the coffeemaker still didn’t come off. I had to disengage snap tabs.
There were two more snap tabs on the side, then the bottom came off. If I was able to fix this appliance, I’d leave out the security screws when reassembling. The snap tabs are enough to hold everything together.
This is what it looks like with the bottom cover off. The digital control board is to the right. See discussion below.

A, the neutral side of the line, connects to the white wire at C.

B, the hot side of the line, connects to D.

D is connected by relay contacts to F. It measured open circuit when the appliance was unplugged.

F goes through a component, probably a thermostat, to G. The DVM showed open circuit between F and G.

G goes through a mystery component to H. The resistance of the component is nil, and is the same both ways, so it’s not a semiconductor. It could be a thermal fuse to open the circuit in case of fire, if the thermostat doesn’t do its job. Between H and J is what appears to be the same thing. If they are fuses, why two of them? Legal issue? Maybe they’re some kind of thermistor to lower power consumption once the pot is brewed, and just being kept warm?

C to J is the heater element, 36 Ω when measured cold.

All of the above I was able to determine without plugging the unit into the wall.

I was hoping for a fixable failure mode, like a loose wire. Or, if the relay contacts had burned out, I could buy a new relay. Or, if one of the thermal fuses opened up, I could bypass it. If the heater element or thermostat failed, those would be too custom to find replacements for. And no, I’m not going to bypass the thermostat. If it were an emergency situation like war or a disaster, I’d do it, but it would be a fire hazard.

Conclusion: It’s not worth fixing. Is there anything worth salvaging? Yes, the carafe and coffee filter. Electronically, there’s a nice relay that I would have kept in the old days. But not anymore. I took it to Goodwill for electronic recycling.