I need the simmer valve for my Thermadore PRG 366 US - it is discontinued. Any suggestions of where I could find this part?

talk to your gas supplier

Go here: You can see the clearance for the intake and exhaust. Valve clearance for ade 366 Google Search

Have the same problem, Casio PRG-80L reads open. No hints about this in the manual. Nor did Votit's suggestion help. Note that although the watch is old there is clearly power left in the capacitor battery. Ended up accidently ito this mode when resetting the time. Assume the open mode is intended for service, but would just like to exit.

your holes in that burner are cloged get metal brush clean holes out.

Hello.
I have worked on a few of these, and it looks like you have one of the cooktops that you need to take off all of the burner bases with a socket wrench, and remove all of the knobs. (Sometimes the burner base bolts are very hard to remove. I have had to carefully heat them up with my torch in order to get them off. A pain in the neck.) The potentiometer is on the burner valve. I am sure you will recognize it when you open it up.
Always make sure you unplug it before working on it because when you go to put the cooktop surface back on, you may push down on a burner valve activating the spark module and you will get a good zap.
You should be able to buy the part from the following links http://www.coastparts.com/mfgs.asp
or http://www.marcone.com/

look down the shaft of the burner valve(remove the knob). with a very thin and somewhat long screwdriver you should be able to adjust this flame, with the burner on MED hold the shaft of the valve with a pair of pliers and turn the screw slowly( you'll need to hold the shaft tightly because if not you'll be turning shaft and not adjustment screw. small increments yield big changes in flame

take the knob off, and take a very small flat screw driver, and inside the valve, turn it to the left, go slow, and you'll see that it goes down, there ya go

Either the potentiors or the simmer control.

I have the same problem and just took the cooktop apart to investigate. I disconnected the solenoid lines from the simmer controller (that is located under a metal guard to the right side under the burners) and checked them with an ohmmeter. It reads an open circuit, which suggest the solenoid is bad. When I turn the control knob on, I also read about 100V DC on the corresponding solenoid terminals of the simmer controller. I was surprised it was that high for a DC voltage, does anyone know if that is correct? I would hate to spend $90 on a replacement solenoid valve and then have it blow because the controller is putting out too much juice.