# Thermostat on a Truma heater



## 88790 (May 9, 2005)

Initially the themostat on my Truma fire was not working properly getting up to temp but not switching again until a very low temp.

Back to A/S they said this was a problem and fitted a remote stat. Same fault with temps over about 20C.

I have fitted a new wall control unit but no difference.

I just wondered if any body else has had this problem. It will be going back for rectification but it would be nice to know if anybody else has had this problem and had it solved.

Many thanks for any help.

John


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## Anonymous (Nov 10, 2000)

I have read, in the accompanying booklet with my trauma, written in Italian by a Chinese linquist I think, it appears to say something along these lines. Do not use 70 except sometimes but use 50 most times otherwise the elements will fur up and finetto the tempreature.

I am sure this has been helpful :roll:


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## 88790 (May 9, 2005)

I wasn't too clear, this is the room heater used on electicity not the water heater.

Sorry for any confusion!

John :wink:


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## Anonymous (Nov 10, 2000)

No - it was my fault for not reading what you wrote properly. I think it best to ignore what I said because water is not what you need here.  

Should get your answer soon from an expert ...


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## Yorky (May 10, 2005)

Hello John
My heater is the same, it tends to get cold before it switches itself on again, I don't think we'r alone from making enquiries it a common trate.
Try giving Truma help line a ring they are very helpful and a ready to discuss problems over the phone. Rgards Eddie


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## Anonymous (Nov 10, 2000)

We had a similar problem on a rental EuraMobil last year. Changing the thermostat did nothing there either, but I can't remember what they found to be the solution.

Slightly more helpfully, I'd second giving Truma UK a call about this on 01283 528201


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## 88790 (May 9, 2005)

Thanks, I rung Truma and they said it was the controller on the side of the wardrobe and sent me a new one.

Unfortunately no difference! Im stumped on this one.

John


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## arcsystems (May 1, 2005)

Hello everyone, my first post on this forum.
Reading though the replies I was stunned to read Trauma sent a new control switch instead of the 'remote temperature sensor' which is the cure for this problem. The problem being that the original sensor is Incorporated in the switch and effected more by heat at the back of the switch than the living space at the front. This means that although the living space being larger cools down or never comes up to temperature, the sensor only switches back on when the wardrobe/bed-box at the back of the switch gets cold.
The remote sensor comes on the end of a 3 meter lead and should according to instruction be located at shoulder height, the other end of the lead simply plugs into a socket on the back of the fire by means of a 'jack plug'.
Of course if the van, sorry motorhome, is under warranty then the remote should be installed under the terms, i.e. for free
Gary


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## 88790 (May 9, 2005)

Really grateful for your reply, should I assume since the remote sensor has been fitted and I have checked to see it is plugged in, that it is a faulty remote sensor.

My MH is going in for a 'habitation' service soon I will get them to chck this then.

John :wink:


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## arcsystems (May 1, 2005)

The sensor itself is a 'thermistor' which is a resistor who's resistance changes with temperature, resistors in are very stable devices and yours is very unlikely to be faulty. If it is then it is a simple job to take a resistance reading from the plug end and I would guess it should be 25K ohms at 25 degrees centigrade, very much higher or no reading at all and indeed it would be faulty. When you plug the remote in, the plug automatically disconnects the original sensor, if it does not for some reason, they will fight each other and control will be lost or at least erratic. 
When I wrote the original piece I did not realise you had one fitted, (I will have to read more slowly!), the location is quite important in as much as it must be away from any heat/draught source. As I said, Truma recommend theirs to be located at shoulder height and underneath a pelmet is a favourite place, but if it can read the temperature of the air in the van without interference it really matters not where it is located.
Personally I have the Carver version and their thermistor is strapped to the sensor for the gas side which is at the front of the fire and at floor level, in this position the temperature control is perfect. 
Gary


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## 90473 (May 1, 2005)

Should have kept quiet Gary, now you're for it  

I noticed the original prob, ie cooling down quite a bit before coming back on, some time ago but didn't really concern me at the time as we just drank more wine thereby increasing our 'anti-freeze' properties (some very old Austrian stuff we had left over).

I haven't looked for the remote thermistor (incapacitated at present with arm in plaster - yet more cheap wine), but is it likely to be found on 5yr old van with Truma blown air heating ? I know this falls into the really vague category, but humour me anyway, presently bored to tears.

I can get no.2 child to dismantle any bits when he gets home from work later.


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## arcsystems (May 1, 2005)

keng said:


> Should have kept quiet Gary, now you're for it
> 
> I've got broard shoulders!
> I will start by refering you to my sig at the bottom of the page, so I don't know everything about the latest Trauma fires, (I have enough to do with Carver!), except the gas side has not changed since 1981
> ...


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## 90473 (May 1, 2005)

Thanks for the info Gary,

I've downloaded the Service pdf doc and now know it's an S3002 :roll: 

Apparently there's a kit consisting of remote sensor and 4m of cable but gord only knows where it plugs in. The only control box (on the rear of the fan unit), is squeezed against a plywood partition in the base of the wardrobe and there is a multi-pin plug connected to this linking the front panel control switch. 

I've emailed truma uk for further info so it'll be interesting if there's any feedback.

Cheers


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## 88790 (May 9, 2005)

Hi Arcsystems, sorry to bother you further!

I have measured the resistance of the thermistor and at about 20C it was 14K ohms. It has been fitted properly at about 5' high and in no draft.

Is their perhaps another thermistor or cut-out in the control box connected bhind the Ultraheat module?

I tend to use it with the fan speed operated automatically, goes fast when heat is coming out and slow when it isn't, is it OK to use it like this.

Any further observations on your part would be more than appreciated.

John :wink:


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## arcsystems (May 1, 2005)

Is it any wonder if you put Truma though a spell checker you get Trauma?, not wrong are they??
I did say 25k was a guess, never the less I will get my hands on one tommorow and find out for certain. 
Yes there is a second sensor...it's in the control switch, if you look it's behind the dial at the 3 o'clock position and the reason the dial has slots cut in the sides so air can pass though. When you plug the remote in it should disconnect this one, if it does not then you are going to have trouble. I have just put two 25k thermistors in parallel to emulate both being connected and got 17k at 18c (both are 34k at this temp on their own), which suggests yours are both 25k and both are still connected.
Anyway this is still guess work so better to wait till tomorrow, I have had this problem on and off for a year and it's about time I found the complete answer. 
The remote generally cures the problem, my only gripes been the need to buy or at least ask to have fitted, something that should be included as standard.


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## 90473 (May 1, 2005)

Hi guys, (truma / trauma), all I can say is that I got a very nice email reply in less than 12 hrs from Truma UK confirming the model details and type of remote sensor I needed for my heater. I also received detailed instructions on how to fit same and the offer of technical advice at any time.

I know you would do the same Gary, come to think of it I have a Carver Cascade water heater fitted, but more on that later  

The only thing they didn't do was offer me a free one  , but I was given a list of stockists and a mail order stockist to contact.

Thanks again for the info (feel a warm glow all over - it's either a feeling of well being or me bl**dy catheter is overflowing)


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## 88790 (May 9, 2005)

Thanks I know what you mean about Trauma! The sort of thing that can cost businesses money.

I have the later type of controller, Smaller grey with black knob. I am afraid I cannot see into it. Iam hanging on to the old one since I did not get any different response with the new one.

Please remember, I am only an amateur so if what I am about to say is crazy, sorry. I just wondered if, looking at the Ultraheat Schematic either No. 21 Temp Cotroller (125c) or No. 22 Temp Limiter (175c) could be faulty - these look a pig to change though, still hopefully not my problem.
I just wondered if when I had it on 2000w they may get too hot, or are faulty.

It seems strange that it works OK at 20C but not higher.

Thanks once again for your help, I hate not knowing whats wrong, even if I do not have to repair it myself!

John :wink:


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## arcsystems (May 1, 2005)

Well I'm not sure I am any further forward!. I have measured a brand new remote and that was 9.6k in the stores. I took a new style control switch out of a sales van in the slightly cooler workshop and that was just over 10k, which is a lot lot less than 14k?? but it will mean they should be 10k at 25c, although not very good quality. The new switch by the way still has the sensor under the knob but you cannot see it, it's also moved over to the 9 o'clock position because the green lights now at 3 o'clock instead of 12 on the old one. The knob is now un-ventilated so the sensor will either lag behind the room temperature or be more effected by heat at the back than before. If you want to experiment, you can pull this new style knob off, it has quite long and flimsy plastic spindle which goes into the 'pot' at the back so be careful to pull it off square. With no remote or disconnected it would be interesting to see if the system works better with this stat exposed. You might find a 2mm allen key will fit in place of the knob to make adjustments to temperature 
On the fire itself there are two self resetting sensors which make sure things don't get to hot here, I suspect these are numbers 21 and 22 you speak off. It's possible I think with yours, one of these is switching off while on the 2kw setting?.
Some tips I have been told work are, 
1) don't use the 2kw setting unless you have to
2) the room stat doesn't work correctly below 7, it just blows cold
3)At all times on electric, only set the fan speed to 1,1/2 and auto, with the stat at 7 or above.
Well as I said I don't think this has moved me closer to the answer, it all seems daft to me. The room stat not working below 7 suggests there is a design fault which is not being put right. The fan speed set low you would have thought would make thing worse as it allows more heat build up on the over temp stats.
Gary


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## 88790 (May 9, 2005)

Gary, many thanks, I am going to the 'Back of Beyond' tomorrow - its an Adults only site near Ringwood, so I won't be worrying you fora week at least.

I agree with you it seems strange, and I don't think I am the only one with this problem! I guess these resetting sensors could well be the trouble. 

I bet Truma dislike people like me, I put a temperature sensor in the fan outlet to note the temperatutre of the warm air when I am checking this - what else has one to do in the caravan in the eveing?

Thanks once again,

John


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