Technical Truma water heater won't light

[sprie]

The PO told me the water heater worked, but I didn't test it when i bought the van.

I had a Gas Safe guy out and we did a bit of investigation. Not sure if had been a blockage in the gas feed, but if there was, he freed it, as we had gas at the connection next to the heater.

He told me to clear the jet out and try again.

The only way i could do this was to remove the water heater (which was a bit of a pain). I then fed some air into the heater burner and made sure there was no blockage - as far as i could tell, there wasn't.

Anyway, I put the heater back in, but no joy: when i turn it on, i can hear the clicks (which i assume means the igniter is working but no other evidence) but after 8 seconds or so, it goes into error mode on the control panel.

When i took the heater out, it wasn't obvious how to get closer to the burner to investigate. If i remove it again and take stuff apart, what should i be looking for?
Or should i give up and look for a replacement?

 

[AsdaPricey]

I’m not stalking your posts but last year in similar circa I had a Truma C4002 Combi heater/boiler which was not dissimilar in fault. Despite changing many parts and waiting a long time for some to come, it ended up being a parts donor for someone else as I was unable to obtain a couple of parts due to its age and no longer supported by Truma - I stuck in a 12v & 230v water boiler and a separate Truma VarioHeat for the blown air…..I’d be £150 up if only I’d gone that route in the first place

 

[sprie]

I’m not stalking your posts but last year in similar circa I had a Truma C4002 Combi heater/boiler which was not dissimilar in fault. Despite changing many parts and waiting a long time for some to come, it ended up being a parts donor for someone else as I was unable to obtain a couple of parts due to its age and no longer supported b

y Truma - I stuck in a 12v & 230v water boiler and a separate Truma VarioHeat for the blown air…..I’d be £150 up if only I’d gone that route in the first place

I have double checked i have gas up to water heater - i blew the pipe with compressor air, but in the opposite direction. And after test, i know i have gas supply.
Having removed the water tank ( i didn't realise that was easy and gets you access to the gubbins), i can get closer to when i turn the control panel on.
The ignitor is working, lots of sparks, but no gas coming through. I double checked with a hand held lighter - burner does not light and there is no smell of gas.

So no gas is getting to the burner.

Does that mean that the solenoid is dud (item 280 in parts diagram)? or could the PCB be faulty? Or is there another reason?

Is there anything else i can take apart and investigate (all i can see are two nuts, one of which is in the photo under those 2 wires that disappear in, if i undo that, does the burner come out?)

If I knew it was just the solenoid, i could try and source replacement, but then the risk is, its something else (and i repeat your experience).

what do you think?

 

[AsdaPricey]

So my opinion, and it is just that, no judgement, just opinion, whilst there are no regulations stopping us faffing with such items, your questions alone point to the same lack of knowledge that I have. The risk factors involved in an untrained eye rebuilding said item out weighs any financial benefits.

I say leave it - look either for an engineer to repair it for you or replace with something else….

I got £70 as spares or repairs for my entire combi unit and the chap purchasing it was a fellow motorhome with the same unit fitted to an older MH, but he was also a gas engineer who knew what he was doing with it. The bonus for him was a tested PCB, new solenoid and seal kit.

I fitted a Bobil Vans 12v/230v 10l Boiler…for off-grid water it will eventually use Solar dump via the 12v element once I’ve changed the solitary flexi solar panel fitted by the PO. For the moment it’s powered whilst on the move once the habitation battery is charged so when I pull up in a lay-by or when I get on site there’s already hot water….no gas required

That said if your set on a diy repair, there is on the bay E, a place near Stoke that tests some Truma PCBs - they’ve got a good reputation but you can throw £40 at a test just to say it works and then your no further on.

Good luck with whatever you do but please do be careful…

 

[ZaphodB]

If I knew it was just the solenoid, i could try and source replacement, but then the risk is, its something else (and i repeat your experience).

what do you think?

A solenoid (valve) is easily checked , it's only an electromagnet that mechanically operates (pulls) the valve, you could confirm it has a resistance at the terminals with a basic mulitmeter (and report back)

and assuming it's 12volt feed, apply 12volts to it (completely out of situ), listen for actuation click (check 1), and assuming this is the main feed valve to the heater, air should flow when energised with 12volts (check 2)

I'll echo what AsdaPricey says , whatever you're doing be careful, don't use gas at all at this stage , use air to confirm flow.

 

[Googlebot]

How old is your regulator?

They can start to block up and won’t give enough gas to light a high consumption appliance.

Does the hob stay lit with all rings lit and trying to light the heater?

 

[sprie]

How old is your regulator?

They can start to block up and won’t give enough gas to light a high consumption appliance.

Does the hob stay lit with all rings lit and trying to light the heater?

hi. I can light the 3 rings on the hob and they burn fine. Don't know if that is sufficient to show there is enough gas pressure for the heater. When i try and light the heater, i do have nothing else gas going.
I do suspect the solenoid or the PCB.

 

[sprie]

A solenoid (valve) is easily checked , it's only an electromagnet that mechanically operates (pulls) the valve, you could confirm it has a resistance at the terminals with a basic mulitmeter (and report back)

and assuming it's 12volt feed, apply 12volts to it (completely out of situ), listen for actuation click (check 1), and assuming this is the main feed valve to the heater, air should flow when energised with 12volts (check 2)

I'll echo what AsdaPricey says , whatever you're doing be careful, don't use gas at all at this stage , use air to confirm flow.

There are 3 wires that go towards the solenoid that come from the PCB.
Assuming i have taken everything off (i.e. disconnected PCB)
1) i think i would have to apply current at the connector onto the PCB
2) as there are 3 wires, it is not obvious which ones i should apply current to.

 

[ZaphodB]

There are 3 wires that go towards the solenoid that come from the PCB.
Assuming i have taken everything off (i.e. disconnected PCB)
1) i think i would have to apply current at the connector onto the PCB
2) as there are 3 wires, it is not obvious which ones i should apply current to.

Can you show me?

The 3rd wire could well be a switch to signal back to the pcb that the solenoid has indeed actuated/moved (could be active high or low, i.e. referenced to the 12V or gnd).

If you've got a multimeter , use the resistance range to check resistaance of the various combinations of the three wires (and report back)

 

[sprie]

Can you show me?

The 3rd wire could well be a switch to signal back to the pcb that the solenoid has indeed actuated/moved (could be active high or low, i.e. referenced to the 12V or gnd).

If you've got a multimeter , use the resistance range to check resistaance of the various combinations of the three wires (and report back)

There is a red, black and green cable that is in that sheath that goes down to the solenoid.
Testing at the connector, i get continuity between red and black and no continuity to these to green.
So i presume current flows down red (+), and black (-) and green is the signal (which would be what you would guess anyway).

I am guessing that
a) the white block is the coil that get magnetised when current flows
b) the long thin brass bit that is inside the coil should therefore move internally when the coil is magnetised and open up the gas flow.

If i were to apply current down red and black from a battery, if solenoid was working correctly i should be able to look down the main pipe and see it open.
But if we are assuming this part is faulty, it won't move, and i won't see anything.
That would then imply (but not quite guarantee) i need to replace this part.

Thinking out aloud: if i were to leave the coil part off the brass part, and put everything else back on, once i turn on the controller, it should energise the coil. Is there a way to test that? As if it failed the test, that might imply the PCB was faulty.

 

[Twotone2]

Guys, LPG is very dangerous especially in confined places and you really should not be disconnecting gas pipe-work or gas fittings all of which need tested for leaks and complete combustion once the work is complete.

 

[ZaphodB]

I'm expecting some resistance (probably less than 25ohms, but certainly not 0ohms) on one particular combination of those three wires.
This would be the solenoid coil (the electromagnet element of the solenoid) , it must be present.

If there isn''t such a resistance found , then the coil is open circuit (i.e. damaged), or the final wiring to it is broken/disconnected.

Forget about current and the controller etc all of the rest of the system, you're simply looking for that resistance first on the solenoid.... it must be present to eliminate the solenoid.

 

[sprie]

Guys, LPG is very dangerous especially in confined places and you really should not be disconnecting gas pipe-work or gas fittings all of which need tested for leaks and complete combustion once the work is complete.

Hi.
I have turned off both the regulator on the gas bottle and also the appliance master valve. I have arranged for the Gas Safe guy to check everything if/when I have got the heater working.

 

[sprie]

I'm expecting some resistance (probably less than 25ohms, but certainly not 0ohms) on one particular combination of those three wires.
This would be the solenoid coil (the electromagnet element of the solenoid) , it must be present.

If there isn''t such a resistance found , then the coil is open circuit (i.e. damaged), or the final wiring to it is broken/disconnected.

Forget about current and the controller etc all of the rest of the system, you're simply looking for that resistance first on the solenoid.... it must be present to eliminate the solenoid.

I put the connectors back on and turned on the controller.
When i (quickly before the controller went to fail) put my steel screwdriver in the hole inside the coil, i could detect no magnetic field.

However, when i ran a magnet up/down/around the brass solenoid, there was no movement, it stayed shut.

I am thinking there are too many uncertainties/unknowns, and i am best off biting the bullet and getting a replacement water heater.

 

[PuntoHowTo]

How is the unit controllled, how do the safety systems check that ignition has been established

Generally there is a control board that opens a solenoid valve then if ignition is not established in a set time it will error out.

Does the control panel give an error code of any sort?

Ignition might be established by heat or light, if it’s a light sensor then replace it, if it’s a heat sensor or thermocouple replace it, if you cannot work it out, or you don’t know how it works, leave it alone.

I have arranged for the Gas Safe guy to check everything if/when I have got the heater working.

You may well have blown yourself up well before that point, given the assumption being made here is that you’re going to get it working before you get them involved!

However, when i ran a magnet up/down/around the brass solenoid, there was no movement, it stayed shut.

It wouldn’t be a very good or safe valve if you could opened by running a magnet nearby, and it’s this that makes me think you really shouldn’t be playing with it

 

[Twotone2]

How is the unit controllled, how do the safety systems check that ignition has been established

Generally there is a control board that opens a solenoid valve then if ignition is not established in a set time it will error out.

Does the control panel give an error code of any sort?

Ignition might be established by heat or light, if it’s a light sensor then replace it, if it’s a heat sensor or thermocouple replace it, if you cannot work it out, or you don’t know how it works, leave it alone.

You may well have blown yourself up well before that point, given the assumption being made here is that you’re going to get it working before you get them involved!



It wouldn’t be a very good or safe valve if you could opened by running a magnet nearby, and it’s this that makes me think you really shouldn’t be playing with it

The boiler PCB checks for flame rectification which is usually by the ignition lead in older boilers or an earth lead or a rectification probe at the end of the burner then the boiler shuts down if no flame is detected within a certain time usually a few seconds or less as you can imagine you don't want a load of unburnt gas inside the boiler combustion chamber especially LPG which is very volatile.

The issue here might not even be a failed solenoid/thermocouple or sensor etc the boiler might simply be failing to safety.

Sounds as though the OP has other plans now so I'll leave it.