Truma heater problem

[Martyn80]

Hoping someone can help, iam just back from lake district with the van and while we were away we noticed the heater not working properly on electric, i noticed that when i turn the green illuminated dial up it wasnt clicking and heat turning on until it was 25degrees even though it was the middle of the night and only about 8 degrees, also we noticed once it came on it stayed on it wouldnt click back off when up to temperature,also just before we left to come home my wife noticed when she turned on the main heater power switch on the heating came on straight away even though i hadn't switched it on and selected 500 1000 2000v,

IAM thinking its not the 2 thermal cut offsas the heaters still working but just not controllable, could it be the pcm or the actuall green dial/switch its self

We have a newborn baby and really need to be able to set the heater on low and let it click on and off all night

Sorry for the long post but i dont want to buy all the parts it could be if i can narrow it down to a part

 

[Damian]

Quote " Sorry for the long post but i dont want to buy all the parts it could be if i can narrow it down to a part "

Then the simple answer is to get a mobile engineer who knows the system and has the spares to fix it.

However, there are several reasons why the heater is not behaving as it should.
First is the position of the temperature sensor, which is housed within the rotary switch being mounted somewhere near the fire and insulated from the main part of the van, the answer is to fit a remote sensor attached to the gas temp sensor at the base of the fire.
There are a couple of other things it "may " be, but the easiest way and in the long run cheapest is to get an engineer to sort it out.

 

[Martyn80]

Thankyou for your reply Damian ,the temperature sensor in the dial has been mounted in the same place since the caravan was new in 2001 and always worked fine positioned there in the 3 years ive had the caravan, i was thinking of replacing the dial/switch and trying that first as its an easy diy cheap swap,i also thought it could be one of the relays on the pcb thats faulty

Thanks again regards Martyn

 

[Grey13]

https://www.practicalcaravan.com/forum/technical/34996-truma-thermostat#262066

 

[jignc]

This thermostat is not very reliable and is expensive to replace.

I have installed on of these

https://www.ebay.co.uk/c/23020394448
very easy to install and will switch the heating between day and night settings.

we have ours set to 20 for the day and 15 for the night. The origional unit is set to max.
It has two sensors one in the unit and a remote one which is fixed to the gas thermostat in the bottom of the heater.

 

[Martyn80]

I have since bought a new temperature dial (thermostat which unfortunately never worked the heater still only clicks on at 25 degrees

If i bought a remote thermostat can you advise how it connects to the heater as the only wires i can see at the base of the fire are the black and brown ones going to the battery box

Does the remote thermostat get plugged in somewhere near the base or wired in ?

 

[Damian]

Unless you have access to the back of the fire, as that is where the electric part of the heater is located, the remote plugs into a jack socket on the control box and one end clips to the gas thermostat at the front of the fire.
If no access then the whole fire has to come out and for that you really need a qualified engineer to do the work as it involves breaking gas fittings and flue seals which must be renewed on replacement.

The remote is a FY1 , have a look on ebay, or ask your local dealer for one

 

[Martyn80]

Thank you Damian i can get access once i remove the 2 drawers above the fire ,thanks for your help

 

[Damian]

Just be aware, it is a very fiddly job to locate the jack socket, which , if I remember correctly, is on the left hand side of the Ultraheat control box at the base of the heating elements, on the side but right next to an angled piece of metal.
Once located, feed the wire behind the control box to the right hand side and along the floor to the front of the fire, then secure the sensor with a tie wrap to the gas sensor.

 

[Martyn80]

Damian on the left hand side of the box is where the 2 ducting hoses are and they seem to be right against the box,unfortunately once i took the 2 drawers out above the heater theres a 2 " strip of wood that goes across between where the drawers where thats stopping me getting my head through to look properly, i tried there with a torch and mirror with no joy,if it comes to it i might have to cut the bit of wood to see properly ,is it definitely the left side ? As i cant get my fingers on that side due to the 2 hoses

 

[Damian]

The fire as a whole is made up of, from front to back, the gas heater, then right behind that is the electric heater, then the silver metal enclosure, then the TEB fan unit.
The ultraheat elements sit on a rectangular control box directly behind the gas fire, in front of the enclosure so there should not be any ducts in that area, they should be behind the enclosure, away from the direct heat of both gas and electric heaters.

It is not advisable to start cutting anything !!! you will create more problems than you want to deal with.

In my experience there are no modern make caravans that allow access to the unit we are talking about and the only way to get to it is by removal of the gas fire.

 

[Jaydug]

This is a picture of the control box looking down on it from above. It has the cover taken off. The jack plug socket is where I've put the red line on the left hand side.

 

[Martyn80]

Jaydug can you confirm the location of this box for me please?,i think ive got it but a bit confused as Damian has said that its located between the gas fire and the electric fire silver enclosure,however i cannot find it there and iam puzzled why a plastic control box would be situated under an electric heating element ,i have removed the 2 drawers above my heater and put my hand down the back of heater ,there is the fan motor then right down the very bottom is a white/grey plastic box with truma written on it ,i can pull one side of the cover off and iam convinced its the same box as you have pictured ,the 2 duct hoses run up the side next to it for the blown air heating

Is this box on the very back of silver enclosure under the fan motor ?
Its just that if iam right and this is the correct box then there would be no need for me to remove the gas fire just to fit the remote sensor

 

[Jaydug]

As you look down the fire back after taking out the drawers, you're looking at the aluminium fire back sheet. The fan motor and the ducts are attached to it. The electric element is fixed to the front of the sheet, so it's between the ali sheet and the gas heat exchanger. The grey plastic box fixed right down at floor level is the control box, so is on the opposite side to the heating element. The socket that you're looking for is on the left side of the control box (as you look down) about 20mm away from the fire back. Probably the easiest way to find the socket is to feel around with the plug between your finger and thumb.

Maybe this diagram will help: http://www.swift-owners-club.com/support/oem-handbooks/truma/ultraheat.html

 

[Martyn80]

Thankyou jaydug
I was pretty sure that was it as when i removed the cover i could feel the 3 relays and the wires at one side and also the red wire on the otherside

Thats brilliant news i can feel the jackplug hole next to the angled bit of metal ,so ive ordered the remote sensor and heres hoping it fixes my problem

Thanks for your fast reply
Regards Martyn

 

[gary]

No idea how old this post is? but electric heating not switching off is due to one of the three relays showng in jay-jug's picture being permanently stuck on

 

[Grey13]

Hi. Does anybody know exactly what the sensor is. (remote) Is it a PT100 or thermocouple or thermistor or what?

 

[ProfJohnL]

Hi. Does anybody know exactly what the sensor is. (remote) Is it a PT100 or thermocouple or thermistor or what?

In Trumas previous gear they would use a thermistor, I guess principally because thermocouples and PT100 resistance by comparison are expensive, and thermocouples need additional expensive circuitry to create cold junction compensation and output linearisation to produce a reproducible scale. Truma like most manufacturers as sensitive to parts cost and count.

 

[Dustydog]

The three relays are available for £16.99 as a trio.
If one or all are at fault change the lot. But we don’t know this is the real problem . However for less than £20 try it. .
Not sure of the relevance of the last few posts about linearisation etc but I guess these days even the simple things are rocket science

 

[Grey13]

To most people the "sensor" is a thingy on a wire with a plug. However my question was not addressed to "most people" and was "what sort of probe" is used. Technically knowledgeable contributors when discussing the "sensor" type and circuitry understand that linearisation and cjc is an integral part of the input circuit and therefore choice. There is more to a probe than a piece of wire with a plug on it!

 

[gary]

The 'sensor' is, (as is Truma's favourite choice), a 10k @25c thermistior

 

[Martyn80]

Thankyou Jaydug
I fitted the remote thermostat last weekend and iam away in van now and the heaters FIXED all works as it should again