Truma Space Heater on Gas

Sep 9, 2022
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3
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Hi All

Would anyone out there know why a Truma Space heater in my Abbey 416 Vogue 2003 would continue to tick (piezeo wise) once the unit was ignited and functioning?

Regards

Stu198
 
Nov 12, 2021
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Not a very technical answer I'm afraid but, I understand you have to push the knob on the top of the heater in to activate the piezo ignition. Is it possible the knob isn't returning fully maybe due accumulated dust causing it to stick down a bit.
If it was mine, the first thing I'd try would be to pull the knob off and give the stem a squirt of WD40 or similar and then replace the knob and work it up and down a few times to see if it frees up.
Worth a try.
 
Mar 14, 2005
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Hello Stu.

Welcome to the forum.

I presume your heater is a Truma S 3000 series model, These use an automatic electronic ignitor Technically it's a re-ignitor becasue it has a flame sensing circuit built into it which when it detects a flame it stops the ignitor from sparking. It does this by looking for a conductive path to be completed between the spark probe and the grounded burner bar by the flame.

The ignitor is controlled by a small micro switch inside the top of the gas valve . so when the valve is turned on the power to the ignitor is also turned on. But as the ignitor runs when the valve id on and stops when its off suggests this is working correctly.

The fact the ignitor continues continues to run when the flame is present suggests four possible faults.

1. The high tension wire or electrode is damaged loosing the conductive path for the flame detection system (the High Tension spark will jump small breaks which will defeat lower voltages.)

2. The flame shape or position could be wrong - A blocked burner could cause a small or miss-shaped flame preventing the flame from completing the circuit. This is a job for a qualified caravan gas fitter

3. There are a pair of wires that connect the ignitor to the micro-switch. One of those wires ( and I cant remember whether its the brown or black) must be clamped firmly to the grounded base plate of the heater

4. The ignitor could be faulty. This can be easily replaced if necessary, but it tends to be quite expensive.
 
Sep 9, 2022
10
3
15
Not a very technical answer I'm afraid but, I understand you have to push the knob on the top of the heater in to activate the piezo ignition. Is it possible the knob isn't returning fully maybe due accumulated dust causing it to stick down a bit.
If it was mine, the first thing I'd try would be to pull the knob off and give the stem a squirt of WD40 or similar and then replace the knob and work it up and down a few times to see if it frees up.
Worth a try.
Paullus1959

Thanks for the prompt response

I will certainly give that a try

Regards

Stu198
 
Sep 9, 2022
10
3
15
Hello Stu.

Welcome to the forum.

I presume your heater is a Truma S 3000 series model, These use an automatic electronic ignitor Technically it's a re-ignitor becasue it has a flame sensing circuit built into it which when it detects a flame it stops the ignitor from sparking. It does this by looking for a conductive path to be completed between the spark probe and the grounded burner bar by the flame.

The ignitor is controlled by a small micro switch inside the top of the gas valve . so when the valve is turned on the power to the ignitor is also turned on. But as the ignitor runs when the valve id on and stops when its off suggests this is working correctly.

The fact the ignitor continues continues to run when the flame is present suggests four possible faults.

1. The high tension wire or electrode is damaged loosing the conductive path for the flame detection system (the High Tension spark will jump small breaks which will defeat lower voltages.)

2. The flame shape or position could be wrong - A blocked burner could cause a small or miss-shaped flame preventing the flame from completing the circuit. This is a job for a qualified caravan gas fitter

3. There are a pair of wires that connect the ignitor to the micro-switch. One of those wires ( and I cant remember whether its the brown or black) must be clamped firmly to the grounded base plate of the heater

4. The ignitor could be faulty. This can be easily replaced if necessary, but it tends to be quite expensive.

ProfJohnL

Thanks for the prompt response

I will certainly give the list a looking at

Much appreciated

Regards

Stu198
 
Jun 6, 2006
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If the flame stays lit when the gas control knob is released and the ignition box keeps ticking then it’s normally the ignition box, often heat damaged.
 
Mar 14, 2005
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If the flame stays lit when the gas control knob is released and the ignition box keeps ticking then it’s normally the ignition box, often heat damaged.
Good point. And it's why on the older SL 3002 heaters (I don't know it the more modern versions have it) there should be a bent metal plate behind the ignitor block to act as a heat shield.
 
Sep 9, 2022
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3
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Martin

Apprerrply. It has the plate, that is in tact. I am leaning towards a new ignitor.
Will keep you all posted on my results
Regards
Stu198
 
Mar 14, 2005
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Before you spend out on an ignitor its definitely worth checking a few other things first.

One of the recommended maintenance tasks is to periodically remove the heaters from cover(when the heater is turned off and is cold) and vacuum to remove dust etc.

With the front cover off, it's worth just turning the gas control on far enough to cause the ignitor to spark. Look carefully along the run of the two wires between the gas valve and the ignitor. One of the wires should be trapped under a small clamp to pierce the wires insulation and to ground it to the chassis of the heater.

If you see any evidence of the spark jumping to either of these wires, it means the ignitors ground connection has been compromised. Re tighten the wire clamp until the spark can be heard but not seen on either of these wires.

Try relighting the heater to see if it has cured the problem.

If it still continues to spark, then we need to check if the flame detection circuit is actually working. The ignitor uses the conductive property of a gas flame to show when a flame is present. The flame should bridge the gap between the spark electrode and the metal burner bar, and it will ground a high impedance voltage which signals the presence of a good flame.

To do this you will need a length of insulated electrical wire with crocodile clips on each end .

Make sure the gas control is in the OFF position. and clip one crocodile clip to some bare metal on the heater chassis.

Carefully pull the High Tension spark cable off the ignitor bloc spade connection. Keep your hands clear of the spade terminal unless you want a 30kV jump. Don't worry its very unlikely to harm you if you do get zapped but its not advisable if you have any heart problems.

Tune the gas control on enough to start the ignitor. When the ignitor fires you should see the spark jumping from the spade. Carefully take the second crocodile clip and move it towards the HT spade terminal - Don't worry as long as the the other crocodile clip is grounded you shouldn't receive shock. At some point about 5mm from the HT spark should jump to the crocodile clip.

Move the crocodile clip so it touches the HT spade, at which point the ignitor should stop firing. if it continues to operate when the crocodile clip is touching then that confirms the ignitor is faulty. If it stops it proves the ignitors flame detection system is working correctly, and obviously there must be some other fault with the electrode or the burner

As both eth electrode and the burner are inside the working parts of the heater you should not attempt to investigate unless you are qualified to do so.

Some times blowing a compressed air line up through the heaters under floor air intake, might blow out any cobwebs, or other debris. This might correct the problem.

But if not then as its now most likely an internal problem you should arrange to have the heater serviced by an approved technician.
 
Last edited:
Mar 14, 2005
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If the flame retraction wasn’t working it wouldn’t hold flame 🤔
The flame detection I have been referring to is the electronic signal the ignitor block uses to stop the spark. Its totally independent of the Flame Failure Device (FFD) which uses a thermocouple in the flame and solenoid in the gas valve to shut the gas flow off if the flame is lost for more than a few seconds.

In Stus case the FFD is working as the flame is maintained, so its some aspect of the flame detection which controls when the spark generator is active has failed in this case.
 

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