I just thought I'd put a bit more info here. If it doesn't end up helping you, maybe it will help someone searching. At any rate, as already mentioned, the thermocouple (presuming it has one) could be bad. Another thing that can happen is if for some reason the knob is now contacting the surface of the stove (if this can physically happen), then it may not actually be being "held on" for the 20 seconds or so it needs. You can test for this by trying to ignite it with the bare stem (remove the knob). If this is the problem then you can likely modify the knob position slightly to stop it happening.
Here is some info from Force 10 (who make great marine stove/ovens) that might help. I hope it's not too long or "thread clogging." If so I could come back and remove it. This is specific to Force 10 but I think it gives a reasonable overview as well. This presumes a thermocouple equipped stove (not all are in RV's, I don't think).
Remember: The Burner Control Knob must be held all the way in for twenty (20) seconds after ignition in order to heat the thermocouple and allow the gas valve to stay open.
There could be a problem with the thermocouple. The small upright attachment next to the burner on the stove top is one end of the thermocouple. Test operation of thermocouple. A simple way of testing the thermocouple is to ignite the burner with the control knob removed from the valve stem. Using your fingers directly on the valve stem, depress, turn to high, and light the burner. If it stays lit after 20 seconds the thermocouple is working properly. If the burner does not stay lit when using the control knob, it is possible that the knob is contacting the face plate before the valve stem is fully depressed. Remedy this by adjusting the position of the knob on the valve stem.
A thermocouple consists of two dissimilar metals joined together at the sensing end. These metals are in contact with each other only at the point that is exposed to the burner flame. When this point is heated by the burner flame a small amount of electricity is generated. This electric current flows to the other end of the thermocouple that is connected to the gas valve. Here it activates an electromagnet that keeps the valve open. Should the burner accidentally be extinguished electricity will no longer be generated and the valve will be snapped back to the closed position by a stainless steel spring.
If necessary, however, remove the thermocouple following the instructions 1 through 14 below. Lightly sand the end that has been removed from the valve with very fine sandpaper. Replace in the valve and test. If this does not work the thermocouple must have failed and will have to be replaced.
You can also test the thermocouple by removing the end from the valve. Heat up the other end with a torch or another burner on your stove. By using a good quality voltmeter, put one lead on the outside of the thermocouple and the other one on the far cold end. If the thermocouple is okay, it will show a reading on your meter.
If the thermocouple appears to be operating properly after testing, the electromagnet (solenoid) inside the valve which contains a stainless steel spring may be defective and require replacement.
REPLACING THE THERMOCOUPLE Tools Required
- Phillips Screwdriver
- 5/16” (8mm) Open Wrench or Crescent Wrench
- 3/8” (10mm) Open Wrench
1. Thermocouples are made out of two dissimilar metals. One end of each metal is fastened together. When this connection is heated up, a small amount of electricity is created and can be measured between the other two ends of these wires.
2. Two different styles of thermocouples are used. In one style the outside of the thermocouple is connected to a copper tube, which acts as a conductor. The inside is an insulated nickel wire, which at the other end, is separated from the copper by a very small insulating washer. Using a small brass fitting this end of the thermocouple screws into the gas valve, which contains an electromagnet.
3. In the other style the outside of the thermocouple is connected directly to the metal burner housing which is connected to the metal frame of the appliance that acts as a conductor. The other conductor is an insulated wire. Using a spade type connector this end is connected to the gas valve, which contains an electromagnet.
4. When the thermocouple is heated, the electricity generated attracts the electromagnet in the valve and holds the valve open. If the flame is accidentally extinguished, the thermocouple cools, causing the electromagnet to spring back and close the valve.
5. If the thermocouple is not holding the valve open, check first that it is screwed into the valve tightly enough, as a loose connection will not transfer the voltage. If it has been tightened too much, the insulating washer will be crushed, shorting out the thermocouple. Ideally, the nut should be installed finger tight, plus a 1/4 turn with a wrench.
[Removed a bunch of stuff that was very specific to Force 10 ranges]
Be extremely careful when putting the end of the thermocouple into the valve. If you turn too tightly you will crush the insulating washer and need another new thermocouple. Ideally the nut should be installed finger tight plus a 1/4 turn with a wrench. Do not force or cross thread anything.
10. Make sure all gas lines, spark ignition wires, and thermocouples are not touching anything sharp.
11. When it is all back together, mix some liquid soap and water and do your standard test for leaks with your fuel system pressurized, and all control knobs turned to OFF.