Gas Burner not staying lit

[slowdriver]

I have an integrated sink/hob unit, with two burners. It was manufactured by the Italian company - Can. My van is three years old.

Recently the small burner will ignite but after about 45 seconds it goes out whether or not there is a pan on the burner.

It has been suggested that the thermocouple for that burner has failed. Therefore I have:

1. Cleaned the thermocouple (It was not particularly dirty).
2. Removed all debris.
3. I have checked that the thermocouple is in the flame, (it is as close as the other burner, and in any event, if it was not sufficiently close to a source of heat it would presumably send a signal to close the valve immediately after initial ignition rather than run for 45 seconds).
4. I have tried "flicking" the thermocouple as suggested in earlier threads.
5. The second larger burner works perfectly.
6. I have a new, full, French, 9kg bottle of propane.

Three questions:

Any suggestions as to what the problem might be?

Any further diagnostic checks I can make?

Any suggestions for a mobile, habitation/Truma/gas-qualified engineer, in the Oxfordshire area?

[Brian Kirby]

What you have described, both in terms of symptoms and in terms of applied remedies, both indicate to me (not a gas expert!  🙂) that the suggested thermocouple failure is the most probable/logical explanation.

[colin]

We have had this several times in the 12 years of having present van, not once have we had to replace the thermocouple. I wiggle the connections at both ends and this fixes it for a year or so.

[Silicongyro]

I have a 3 burner SMEV unit and have experienced a similar effect on one burner, from time to time.

In a similar manner to Colin above, I "wiggle" the thermocouple protuding through the stainless steel hob surface plate and try to more firmly seat it into the hole - all from below the hob. This always works for a time and I suspect it is the thermocouple body needing a current return via the hob plate and developing poor contact over time.

[slowdriver]

Apologies for the tardy response to all three of you. Many thanks I will try the "wiggle" technique and see if that fixes it.

[Basil]

For information, I am unable to explain the reason that wiggling the thermocouple makes it work, unless guessing, it repositions the flame contact position or re sets a 'dirty' connection at the tap end. However I can definitely assure you there is no earth return as a thermocouple is a concentric wire, i.e. one wire within another, made from two dissimilar metals fused together at the heated end. It is this that creates a small EMF that operates an electromagnet within the tap. A loose, dirty or poor connection at the tap end would give problems, as would the heated end not being correctly placed in the flame. It can be too hot or too cool if out of position. Most likely though it's likely to be on the point of failure.

Bas

[slowdriver]

On 29/08/2023 at 12:42, Basil said:

For information, I am unable to explain the reason that wiggling the thermocouple makes it work, unless guessing, it repositions the flame contact position or re sets a 'dirty' connection at the tap end. However I can definitely assure you there is no earth return as a thermocouple is a concentric wire, i.e. one wire within another, made from two dissimilar metals fused together at the heated end. It is this that creates a small EMF that operates an electromagnet within the tap. 

Well, that's very odd then because  I finally got this sorted today in France at Emeraud Evasion (a La Strada dealer) in Dinard across the river from St-Malo, at no cost! https://www.emeraude-evasion.com

It would "appear" that the Italian Can integrated sink and hob unit uses the body of the hob as earth and therefore the body of the thermocouple needs to be in contact with it in order to reliably operate. Cleaning the thermocouple itself may work but only if you make sure there is no build-up of grot between the hob base, (which is about 1- 2mm thick) and the thermocouple body. We live in a hard water area and calcification is a regular issue on anything metal.  In this instance, the layer of calcium wasn't obvious when looking from above but nevertheless was there. The dealership owner cleaned it out with the point of a Stanley knife from above and it did the job. He did not reposition the thermocouple in relation to the adjacent flame. So if removing the calcification fixed the issue and yet the hob body is not used as a return current then there must be another explanation as to why this cleaning and wiggling solution is the most commonly proposed. Maybe the thermocouple touching the hob via the calcification interferes with the circuitry and cleaning it eradicates the problem?

He indicated this was something they see reasonably often on various different makes of van. 

[onecal]

Hi

Strange is your Can gas burner a PV1351 model?