repairing coffeemaker, Diode, zener, resistor?

[TheNewLab]

Hi, I have gone through three coffeemakers within the last month or so. each one have been in service for many years.
Each one only the heating plate are the failures. they just stopped heating the plate at all. each one is a different brand.
First, I suspect that the failures are caused by electrical surges. The GFCI failed testing about a year ago, and I never got around to replacing it.
1.) will replacing it prevent the power surges?
2.) the diode, zener, resistor: look like a diode. I tested as a diode since all have at one end the markings. however reading another post mentioned a resistor. I thought the heating coil itself is a resistor and the diodes somehow control the AC current flowing through. (my guess)
3.) where do I find coffeemaker diodes, whatever they are. I have the part numbers. I am afraid to look on ebay dispute maybe having the best price. I paid a lot of money for two of them and the electronics are in fine in both. They just will not heat up.

Any suggestions of where to find parts, Anyone want to educate me on why, what (I) suspect are diodes are used at all in the heating plate?

[Nusa]

1) GFCI is intended to disconnect the circuit quickly when it detects a short to earth. Such as if you were being electrocuted. It's purely a safety device, and is not a surge suppressor of any kind.

2,3) Whatever it is, you'll probably get better results if you post pictures and identification numbers, and why you think it's failed if it's not obvious. You're speculating without actually giving us any information to work with. Yes, heaters are generally resistors, and they usually work as well on AC as they do on DC.

I'd suggest measuring the resistance of the heating element. If it doesn't have any, then that's clearly the failure point. Unless the unit was designed with a replaceable heating element, odds are it's not economical to repair.

[Gregg]

Many home appliances for the US market have thermal fuses that disconnect the heating element or possibly control power also.  They are combination safety devices that will open a circuit on over temperature, over current or both. They are generally rated in degrees C, Amps and max voltage.  The temperature selected by the manufacturer can be different than the operating temperature of the appliance because of the location of the device; they are often somewhat thermally insulated from the highest temperature locations, sometimes in a fiberglass sheath or even shrink tube.  A quick Google search for thermal fuse will bring up some nice pictures and sources.  The ones direct from China may not be a bargain.

[PaulAm]

I had a little counter top espresso machine that quit working and it turned out to be the thermal fuse.

Once that was fixed it turned into a longer range project to add a PID controller and temperature readout.

Then I fixed it by getting a commercial espresso machine