Gas fire wont stay on after initial ignite

[Djupp01]

Hi all joined this group for my dad. Hope someone can help please.

Got a problem with his gas fire in caravan basically when he pushes down ignite switch to light main burner the pilot light ignites fine but soon as he releases the switch it goes out. He can even jam the switch down for 2hrs plus but soon as u un jam the switch it still goes out and mian burner will not light and stay on. Any ideas please as want to get it sorted before holiday in few weeks.

 

[Damian]

It sounds like the thermocouple is faulty.
As the thermocouple is an essential safety item you would be best advised to get a mobile engineer to repair it for you.

 

[Gafferbill]

I agree with Damian.

The thermocouple, when working properly, detects the heat from the pilot light flame and allows a gas supply to reach the main burner and the pilot light, allowing the gas fire to operate normally.
If it doesn't detect this heat it cuts the supply to the main burner and the pilot light and thus as Damian says is a safety device stopping the flow of unburnt gas.
Since there is no heat in the system before start up this safety system has to be manually overridden in order to initially light the pilot light .
This is what you are doing when you push down the ignite switch and hold it down until the thermocouple reaches its operating temperature.
You need to get the fire looked at by a qualified technician..........replacing a thermocouple should not be that expensive.

 

[bertieboy1]

Might not be a faulty a faulty thermocouple,could be the thermocouple has been knocked or moved so that the flame doesn't impinge on it.You don't need to be qualified to see this and move the T/C over the flame if necessary.

 

[ProfJohnL]

Might not be a faulty a faulty thermocouple,could be the thermocouple has been knocked or moved so that the flame doesn't impinge on it.You don't need to be qualified to see this and move the T/C over the flame if necessary.

Sorry Bertie,
But I cant agree with you. Firstly the thermocouple is pretty substantial component held in position by a nut. Its really hard to see how it could have been "knocked" and moved without some pretty substantial other collateral damage having been caused. If that were the case the fire would need professional attention.

Secondly to gain proper access to the burner end of the thermocouple requires dismantling the burner housing, which is the part where its best to leave the work to competent fitters.

Thirdly, the position of the thermocouple is fixed by the position of its mounting bracket which allows for minimal repositioning.

Thermocouples can age and go faulty especially, or sometimes if the burner pattern is wrong the thermocouple tip can be over heated and damaged.

The component I suspect you are referring to is the ignition electrode, which is more vulnerable. However if the electrode was not in position the fire would not ignite,the fact it does light rather discounts that as the problem but that has nothing to do with the thermocouple in conjunction with the electromagnetic capsule in the gas valve which forms the Flame Failure Device.

 

[Gozza]

Hi all

Resurrecting this thread as I had a similar problem at the weekend.

Arrived on site Saturday, tried to light the fridge and it lit OK, but went out as soon as I let go of the thermocouple over-ride button. It happened several times, in the end I gave up and decided to live without the fridge until I could fire up the generator on Sunday morning.

Gas cylinder is half full and all other gas appliances were working OK. The fridge worked fine on gas two weeks ago when it ran on gas all over the BH weekend.

My first thought, based on a rough memory of this thread, was the thermocouple. However when researching the subject on line last night, someone on another caravan forum said they'd had a similar problem which they resolved by cleaning the mains / 12v / gas selector switch with some switch cleaner.

Any comments from my knowledgable chums? Does this selector switch thing seem likely? I could do that myself as I'm competent through having a City and Guilds in electronics, but if it's likely to be the thermocouple then I need to book a gas engineer soonest as I need the fridge to work on gas in three weeks time!

Cheers all, Gozza

 

[Damian]

How old is your van?

 

[Gozza]

About 12 years

 

[Damian]

Quite often on older vans the thermocouple override in the gas knob wears the inside of the knob so that when pushed in to light the gas, it does not push the override in far enough.
Try taking the knob off (it should just pull off) and press the spindle in as you light the gas, hold in for 20 seconds and it should stay alight.
If it does, put a small packing piece in the knob spindle socket to take up the wear.

 

[Gozza]

UPDATE - I wasn't able to look at the fridge between the last event and this weekend's, owing to the person I was loaning the van to leavingso much junk in there between loanings that the fridge wasn't accessible :-(

So we got the van on site, emptied out all the junk...sorry, top quality safety equipment...and I cycled the mode selector switch a few times vigourously, mains/gas/mains/gas/mains/gas. Did the usual with the thermocouple override and low and behold, it lit and stayed on! Happy Gozza!
Add to winter task list...attack selector switch with a can of switch contact cleaner.