Pw9crab9
Free Member
Hi can any one help smev gas hob 2 burners work ok the other will light but when you release the button the gas goes out
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That’s right.It sounds like the thermocouple but it could be the knob, although not likely, try taking the knob off and pushing the shaft in as you light it, if it still goes out it's the thermocouple. Check the tip of the thermocouple is in the flame, if so it wil need replacing
How do magnets in the knob sense the flame?I have a Thetford and had the same problem with my grill mine doesn't have a conventional Thermocouple it's done via magnets in the knob, so I had to have a new one. Yours may be the same if you cant see a thermocouple by the flame.
No idea how idea how it works but I do not have the normal thermocouple just the Pizzo spark probe by each gas ring, maybe uses that somehow. When the engineer fixed it under warranty I'm sure I remember him saying the cut off was part of the control valve and worked by magnets or it may have been electro magnetic.How do magnets in the knob sense the flame?
That is how a thermocouple works, if your hob doesn't have a thermocouple then it will have a flame sensing ingnition electrode, do you have to hold the knob in when you light the burner?Pausim You got me wondering so did a bit of digging and got the below of internet. I'm confused as I'm sure my cooker hob rings don't have traditional thermocouples, well none I can see when I lift the lid. Anyway I was correct about magnets albeit electro magnet.
How the system works,:
There is a valve within the tap assembly that contains a coil, this coil becomes a magnet when current from a heated thermocouple is passed through it, this is why when you light the burner and release the tap immediately it will go out.
Holding down the tap for 30 secs or so has to be done to hold the valve open until the magnetic field is sufficient to hold it open, the thermocouple produces around 25mv to 35mv DC ( millivolts ) open circuit and about 15mv to 20mv closed circuit.
Presuming your thermocouples are single wire, current flow when the thermocouple is heated is through the wire to coil in the tap assembly, the return, earth is through the tap body, hob and to the thermocouple body.
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Yes I have to push it in turn it then press the spark button don't think I have to hold it in once alight.That is how a thermocouple works, if your hob doesn't have a thermocouple then it will have a flame sensing ingnition electrode, do you have to hold the knob in when you light the burner?
Then it's a thermocouple. A thermocouple has to heat up on order to generate the electricity to energise the electro magnet, an electronic system is instant,also I have not seen that type of control on a hob.
Likewise result for me and it was easy access after I removed the cutlery drawer.Usually a bad connection on the wire underneath, if you can access the underside give the terminal on the offending burner a wiggle. Works for us.
DP
Our oven did exactly this, removed the knob and pushed the shaft in using then lit the flame, held the shaft in for 5 seconds then bingo the flame stayed on.It sounds like the thermocouple but it could be the knob, although not likely, try taking the knob off and pushing the shaft in as you light it, if it still goes out it's the thermocouple. Check the tip of the thermocouple is in the flame, if so it wil need replacing
That’s right.
Sometimes we used to roll a small amount of paper and put it into the knob. When pressed it would make a better contact the hole may be too deep in the knob. Best check is using the knob off another burner. If ok with that then put something in to allow it to press the shaft making it contact with the thermocouple.
Also at burner make sure thermocouple is in the flame.
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