Gas oven reluctant to heat up.

[Chris French]

Hi folks,

Our gas oven (New World, 20+ odd years old) is being reluctant to heat up.

Old behaviour: Turn knob oven to required setting, a bit of clicking, flame lights, few seconds and then it grows top full size , heats up oven.

New behaviour:

Turn on, flame lights, just sits there indefinitely on low, oven doesn't get very warm. However if you open the oven door after the flame lights, after a wait (10-20 seconds?) the flame goes to full size, shut door and oven heats. It seems to be heating it to the correct temp.

There is an additional quirk. If the oven is used at a higher temp (say Mark 6), then reduced to a lower temp (say mark 4) the flame doesn't kick back in to warm up again the oven once it's cooled down past mark

2. I had a peer in the back of the oven and can't see anything obvious. any thoughts folks?

Thanks

[Tim+]

I was gonna say that the main thermostat that regulates the gas must be faulty but then I saw this.

Could be either I suppose.

Tim

[Fredxxx]

I had assumed it was the Flame Failure Device.

If it is the New World oven I think it is, there is a shield in front if the burner that can be removed. Check the integrity of the burner, I suspect some food crud has dropped onto the burner, possibly now carbonised and has blocked some holes.

[Bob Minchin]

I've no relevant experience on gas ovens but I'm surprised that any flame failure device would allow and gas to continue to flow?

[DerbyBorn]

I seem to recall that some ovens have a device to turn down the gas when the door is opened. It sounds like yours has this - and it could be sticking or failing.

I believe it is to prevent the heat from taking off your eyebrows when you open the door with the burner on full. It may also be an anti-suicide device!

[Chris B]

I think on my gas oven the FFD and thermostat seem to work in partnership.

1) Turn on oven - no flame but series of sparks from igniter across part of the burner. 2) small "pilot flame" springs into action that seems to be directed towards a small bulb- but no flame from the main burner 3) About ten seconds later big "wumph" as main burner lights. 4) when oven up to temp main burner flame is very low but much bigger than in (2) above.

In (4) I assume that the FFD is open but thermostat turned right down. in (2) I assume that FFD is initially closed but Thermostat would be fully open.

[Chris French]

In message , DerbyBorn writes

Thanks,

Butl it has never turned down the flame before. So it probably hasn't got that function.

[Chris French]

Mine works in a similar way except it doesn't have a pilot flame, it just seems to light the main burner at a low level (as it is when the oven is up to temp.) then it turn the flame on full.

I did wonder about a faulty FFD, but couldn't work out what failure mode would lead the observed behaviour (will light once the door is open, but not if it shut. The flame is behaving the same. Unless there was some sort of oxygen sensor as well?

[Robin]

Me neither. But I did just wonder if the FFD/FSD is very near to [total] failure but not quite there yet. So opening the door increases the air supply, and that allows the "pilot flame" to heat the tip of the device just that bit more, and so open the valve to pass gas at the full rate.

I have tested this in the past by turning on the oven and then applying a bit more heat to the tip using a long gas lighter - one like this

But I am sure that was foolish behaviour so cannot possibly recommend it.

And it still doesn't give a convincing explanation as to what happens when the thermostat reduces the supply.

[philipuk]

If it's that old, time for a new one?