Truma S3002 gas heater problem: battery ignition starts ticking when fire heats up. (1 Viewer)

[The Nomad]

Truma S3002 gas heater problem: battery ignition starts ticking when fire heats up....

On our year 2001 Benimar Motorhome we've got a Truma S3002 gas fire. Gazillions of these heaters are in use in motorhomes and caravans all over the world.
Ours is the basic model, which just operates on gas (it doesn't have the optional electric heating element inside the front cover.) I'll try to attach a stock photo of our model type of heater below.

As owner of these heaters know, you can operate it just as a convection heater, or you can use the fan, either on constant velocity or automatic, to blow warm air from it through ducts around the motorhome.
But we have a slight problem with ours.

It always starts erfectly, first “tick” of the battery ignition.
On convection only (no fan), if I set its temperature dial (which goes from 1 to 10) to anything above 3, then after the fire heats up....maybe after 10 minutes or so...the battery ignition begins constant ticking. If we turn the fire off, it stops ticking immediately. If we let the fire cool down, then re-ignite it starts and runs perfectly until it reaches whatever is the “ticking threshold temperature” then starts ticking again.
If I set the temperature dial at 3 or below, it'll run like that all day – but of course it doesn't give out so much heat, as the thermostat cuts it back from full burn to just tickover sooner.

We get the same problem if we use it for blown-air round the Motorhome via the auto fan. We set the fan speed to 5 (max) and the fan setting to Auto, so the fan increases in revs as the fire warms up.
If we set the temp dial to above 6 (out of 10), then eventually after maybe 20 minutes or so, we get the constant ignition ticking happening. Turn off, allow to cool, start again and all's fine for a while again.
But if temperature setting is at 6 or below, it'll run all day. But not very warm.

Our workaround this is of course just to keep the temperature settings below the “ticking threshold” dial settings.
This is fine, but there are times when we'd like to make the fire work a bit harder, to get the temperature in the Motorhome a bit higher.
I spoke to a motorhome dealer about this a while ago and he just replied that “ yes I've heard a lot of them do that Sir”.


So........for others who have ACTUALLY EXPERIENCED the same behaviour from their Truma S3002 (or S5002) gas heater, what did you do?
Continue to live with it?
Remove the battery compartment and fit instead one of those piezzo push-buttons, connected to the ignition spark wire?
Break into the existing circuit from battery to ignition spark terminal and fit a simple switch to allow battery to be isolated after ignition?



Whilst I know this is a really helpful group; I reckon it would be best if specifically only those people with a good technical knowledge of this exact gas heater and/or who have actually experience this exact issue could advise, rather than everyone else offering well-meant guesses as to what it might be.

Many thanks.

 

[Just smiffy]

I would change the thermocouple first as it sounds like a temperature problem, that would be a cheap option too..

 

[JJ]

Okay.

First let me state I do not KNOW exactly what is wrong with your heater.

However I have removed, stripped down and overhauled my 5002 in a 1987 Hymer 660 so will offer these thoughts.

Mine... as you probably know... is the double unit heater but basically the same as yours except it has two units side by side.

The ticking you get is the ignition trying to light the flame. It should only do this if the gas has run out and the fire has cooled down.

So, as Gary says above, I reckon the thermocouple thingy is faulty. Yours obviously "thinks" the fire has cooled down when it hasn't.

I don't know what van yours is in or whether you will be doing the fixing yourself, but on my Hymer you can reach the burners and stuff by removing a plate underneath the van.

Being rather inflexible, I chose to remove the whole heater from inside the van. This was a straight forward job on mine.

I think it might be possible to get to the thermo couple without removing it all though.

Your idea of a switch seems like a possible "work around" but I would be a tad reluctant to mess about with a faulty thermo couple in a gas appliance.

I would definitely ask Google first and you might find all you need to know there, probably with YouTube how to do it videos as well.

JJ

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[The Nomad]

OK guys - many thanks for the info.

But I'm struggling a bit withe the diagnosis of a fault with the thermocouple.......

MY understanding was that a thermocouple sends a yes/no signal to the gas valve, not to the ignition module. (Is my understanding wrong?)

As the fire is lighting fine and continuing to burn OK then it seems to me that the thermocouple is certainly getting enough heat to keep it's inside part expanded and thus keep sending the "keep gas valve open" signal to the valve at the bottom of the on/off/temperature setting control rod.

There seems to be something happening/changing in the electrical circuit of ignition module/battery box and the spark igniter when a certain sufficiently high temperature is reached, that suddenly causes the ignition box to think that a spark is being called for by the spark igniter - but I've no idea what!

At the moment I guess that other than splicing a simple toggle switch into the cable between them so that I can turn off the connection between then once fire is lit, my only other (a lot more expensive!) option is a new ignition box at getting on for 60 quid.....

 

[Teuchter]

If you can isolate the wire that only feeds the spark igniter and NOT the gas valve then a remote switch would IMO be a good solution!

 

[JJ]

I think you will find, at the bottom of the rod holding the the twisty control knob, there is also a switch which switches on the ignited. It too has a heat sensor thingy which switches of the ignition once the burner fires up... I am pretty sure this is where your problem lies...

But please remember, I am not an expert...


JJ

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[dave newell]

When the "ticking" starts can you still see a flame in the window? If yes then the ignition module probably needs replacing. The thermocouple controls the gas valve, the ignition is controlled through "flame rectification". The ignition module is not terribly expensive and is very easy to replace . The fire would also probably benefit from a good clean and service.

D.
https://www.leisureshopdirect.com/g...iter-for-trumatic-s3002-s3004-and-s5002-s5004

 

[tonyidle]

The thermocouple has only one function and that is to cut-off the gas at the gas valve shortly after the flame disappears. It isn't connected in any way to the ignition arrangements. This statement applies to any caravan or motorhome LPG heating system. The spark ignition senses the presence of a flame (ie burner lit) using the ignition electrode which is itself just a simple metal rod. From your description of the symptoms either the tip of the electrode isn't always in contact with the flame or the ignition module is faulty.

Check that the flame near the electrode isn't distorted by debris on the burner, that the burner jet is clear, and that the ignition electrode bracket attachment screw is tight. If everything in that area looks OK try a replacement ignition module.

From another manufacturers site:

"Once a gas burner ignites a resistance is created between the electrode (igniter) and the burner.

• Any change to this electrical resistance, increase or decrease, causes the electrode to attempt a re-ignition; this is normal operation.
• Igniter clicking with a non-operational burner may indicate a decrease in electrical resistance.
• Igniter clicking with an operational burner may indicate an increase in electrical resistance.
• Common issues that cause an igniter to click after ignition include:
  • Increased or decreased gas pressure
  • Increased or decreased airflow over burner
  • Wet electrode or burner
  • Burner assembly out of alignment"

 

[The Nomad]

When the "ticking" starts can you still see a flame in the window? If yes then the ignition module probably needs replacing. The thermocouple controls the gas valve, the ignition is controlled through "flame rectification". The ignition module is not terribly expensive and is very easy to replace . The fire would also probably benefit from a good clean and service.

D.
https://www.leisureshopdirect.com/g...iter-for-trumatic-s3002-s3004-and-s5002-s5004

Many thanks Dave -

Yes there's still the flame burning as normal when it gets up to "X" temperature and the ticking restarts, so I too think it's an electrical/electronic control fault not a gas problem.
Adding to that conclusion is that if I start the fire on temperature setting "10", the burner is going at full chat, yet that big flame and thus possible "flame lift" from the surface of the burner) doesn't in itself cause the igniter to start ticking again. It's only after perhaps 10 minutes that the ticking restarts at high temperature settings.
And if we keep the temperature dial towards the low end of the range (say 3 on radiant heat, and below 6 on fan assist blown hot air), the main burner kicks in and out as required to get to and keep the set temperature, without ever causing the igniter to start ticking again.
It's as though the auto ignition box of tricks gets overheated if the fire is set to run really hot, and it's that which causes it to start constant ticking once it gets up to "Fault temperature"

I've been on to Truma UK today and having explained to them exactly the symptoms that I posted above, their Techie guy also reckons it's a fault with the auto ignition box.

They are unfortunately not repairable, and new one are NOT cheap though, at more than 80 quid retail from UK Truma parts distributors! About the same price new from ebay sellers.

So at the moment I'm researching other workarounds too, such as either splicing a simple on/off switch into the black or brown wire that each lead from the auto ignition box to the gas valve (which is operated from the metal control rod), so that we can turn off the ignition function once the fire is lit.

Alternatively, someone has suggested simply removing the battery from the auto ignition box to thus disable it, and instead fit a simple push-button piezzo ignition into the lid, with a wire from that straight into the high tension wire that leads out of the middle of the back of the ignition box to the actual spark terminal inside the fire on top of the burner. The older versions of this gas fire apparently had that rather than the fancy (ie complex and expensive) battery propelled automatic igniter system.

A third option is to fettle up from some ally sheet a much better heat shield between the auto ignition box and the flue pipe from the fire which passes right behind it.

So, plenty of things to play around with in the coming days!

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[dave newell]

It doesn't matter what the temperature dial is set at the flame will be the same, it is simply on or off. I don't think £80 odd is that expensive personally and i recommend you fit a new one to fix the fault properly rather than bodging about with "workarouds"

D.

 

[JJ]

It doesn't matter what the temperature dial is set at the flame will be the same, it is simply on or off. I don't think £80 odd is that expensive personally and i recommend you fit a new one to fix the fault properly rather than bodging about with "workarouds"

D.

I hate to disagree with a professional, and maybe more modern heaters are as stated above, but my temperature dial definitely reduces the size of the flame... definitely... (I think).


JJ

 

[two]

What I recall of these heaters (from 1990) is that they are largely mechanical, just like a gas oven. The electronic ignition is an independent add-on (as is the fan distribution at the back).

I’d try removing the batteries after ignition and seeing what happens then. It might, at least, confirm if it’s that box of tricks or not and then you can decide what to do about it.

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