Posted: 17 July 2009 7:22 PM Subject: truma trauma
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the truma heater in my 04 adria has stopped blowing hot air, but still heats the water. having had it checked out i was told that it works when the PCB board is by-passed. a new board was quoted by a supplier (adria or truma) as costing £300. Wow! does anyone know if there is an alternate source, or option???
PCBs for Truma C-Series combination air/water heating appliances have always had a savage price-tag, which might not be so bad if they also had a guaranteed 20-year life-span!
A faulty PCB is treated by Truma as a disposable item. As far as I'm aware, Truma does not offer an exchange or repair service for PCBs and, as the boards are only available through retailers of Truma products, it's hard to see how a 'cheap' PCB can be acquired. (If you do chance to see a C-Series PCB being offered for sale on (say) e-bay, be aware that that different model Truma C-Series appliances require different printed-circuit boards.)
I've never heard of a faulty C-Series PCB being successfully repaired and I don't know of anyone who would attempt the task. It's quite possible (as hallii suggests) that, when a board develops a fault, the problem can be minor and, in theory, easily rectified. However, I don't think circuit diagrams are available for Truma PCBs, so fault-diagnosis may be difficult and time-consuming unless there is clear visual evidence of component failure.
The fact that the water-heating side of your appliance still functions indicates that there's unlikely to be any problem with the gas-burner. I presume that "it works when the PCB board is by-passed" just means that it has been confirmed that the blown-air fan will run when 12V power is supplied to it. The diagnosis that the PCB is the culprit is very probably correct, as it's well known that they can and do fail, but the proof of the pudding will be when a replacement PCB is installed.
Posted: 18 July 2009 10:46 AM Subject: RE: truma trauma
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thanks for yourr input folks. i'll check out the links you provided, but i fear derek may be right and i'll have to sell my body to get a new one (board not body!). what i cant understand is how the engineer could bypass the board and make it work.? why cant it be wired without the board??
Posted: 19 July 2009 12:18 PM Subject: RE: truma trauma
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You could ring Truma (UK) Ltd, direct and book your van in to their service department at, 2000, Park Lane, Dove Valley Park trading estate, Foston, South Derbyshire. DE65 5BG. It's, between Derby and Uttoxeter off the A50. Or just give them a call to get confirmation of what the problem could be and if it is actually possible to by pass any part of the ECU. Tel. 01283 586014 Fax 01283 586029. Yes i realise it's a long way but you could combine it with a visit to the nearby Peak district.
Try Sargent Electrics at Beverley, they will be able to advise you one way or another.
I'm not arguing with your statement: I'm just surprised that you think Sargent Electrical Services would be able to to provide definitive advice on a problem with a Truma appliance - or, at least, to provide advice that would match the expertise available at Truma(UK).
Posted: 23 July 2009 10:19 PM Subject: RE: truma trauma
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just to keep you helpful friends informed, my engineer said that the fault was no 12v output from the board to the fan. so whilst i investigated the cost of a new board (i had a quote of £300) he inserted a switch to provide the 12v. this appeared to do the trick, but unfortunately after a while is showed an error state (the red light on the control switch).
i took the vehicle back, and they disconnected the switch whilst they investigated the reason for the error light. and it all worked as it should??? dry joint? dodgy earth? dont know, but im watching it with interest.
The electronics of Truma combination heaters have become increasingly complex as extra 'safety related' functionality has been added.
A motorhome dealer recently told me about a vehicle with a Truma C-Series heater that was working OK when heating water, but blew the 12V-supply fuse when blown-air heating was selected.
If you take your motorhome to Truma(UK)'s HQ, they have a test-bench on which C-Series problems can be diagnosed, plus a ready supply of spare parts (like PCBs) that can be substituted during the diagnostic process. But such luxuries are unavailable to motorhome dealers and, when a heater has been squeezed inaccessibly into a tiny cupboard (as it often is), initial fault-finding tends to rely on educated guesswork based on whatever limited testing it's possible to carry out with the appliance remaining in situ. In the above case it was concluded that the heater's fan-motor was faulty.
A new fan-motor was ordered and (with the fan not fitted) temporarily connected to the heater's wiring just to confirm that the diagnosis had been correct. Blown-air heating was selected, the heater started up, the motor ran for a short period, then the heater performed a safety shut-down with the red error light coming on. The procedure was repeated and, each time, the same thing happened.
The dealer contacted Truma(UK), saying that there seemed to be something peculiar about the new motor he had been sent and was told "Yes, that happens and it's caught us out in the past". Apparently C-Series appliances, when in blown-air mode, are able to detect when there is inadequate air passing through the heater (eg. the fan motor isn't functioning correctly) and will shut down to prevent overheating.
The heater was now displaced from its tight-fitting enclosure to allow the new motor to be fitted. The old motor was removed and, out of interest, the dealer connected it to a 12V power supply - and it worked perfectly. A closer inspection revealed that the problem, in fact, related back to when the motorhome had originally been built.
It's common for a C-Series appliance to be installed in a motorhome with its blown-air fan positioned in a rear corner of the heater's enclosure. In this instance the back of the fan motor was virtually touching a bulkhead and one of the motor's 12V power-supply cables had been trapped between bulkhead and motor. This might not have been important, except for the fact that the motor's central shaft protrudes slightly through the motor's rear face. After a time the rotating shaft wore through the cable's insulation, causing a short circuit and blowing the fuse. Simple really!
Posted: 25 July 2009 7:07 AM Subject: RE: truma trauma
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my final bill was around £140, but i cant give a definitive cost, as i was having a number of small jobs done at the same time. the hourly rate was £40.
i testeed the ssystem the following day, and again had problems. the fan againn wouldnt wwork, but i found that the tapss haad aan air lock. as ssoon as this was clearedd, the fan cut in. i tested it again a few hours later (after the heater had been off), and it took ages before the orange lamp (water being heated) went out. the fan didnt cut in til this lamp extinguished. but i am sure that whilst browsing the operating instructions, i had read something about a relationship between the heating of the water and the air temperature. the air temp. was such that you wouldnt normally use the fan heater. i will continue to check it, and give it a good test. the engineer is on standby!!
excuse thee badd speelling, this laaptop keyboardd is increeddibly sensitivee and doublee taps ( or im a rubbish typisst!))
It might be useful to know which variant of Truma C-Series heater your Adria has. Being a 2004 motorhome, it's probably a Truma C-3402 or a C-6002, but it could be helpful if you are able to confirm which one.
There is no direct relationship between a C-Series heater's water-heating system and the air temperature, nor should an air-lock in the water system have any impact on blown-air heating.
I suggest you try the following test...
Turn the room-temperature rotary switch on your heater's control-panel to its maximum setting (ie "9") and select blown-air heating. Unless the air temperature in your motorhome is like that of a blast furnace, the heater's blown-air fan should begin to run at a low speed and the heater's gas-burner should light at its lowest heat output (2kW). If the temperature in the motorhome is already high, the heater will continue to operate at low fan speed/2kw gas output until the original air temperature has been raised to match the setting that was selected via the rotary switch ("9"=swelteringly hot). At this point the blown-air fan will shut off. (If blown-air-only has been selected, then the gas burner will also shut down. If blown-air + water heating has been selected, then the gas burner will continue to operate at 2kW output until the temperature of the water has reached 60°C.)
At more normal UK air temperatures (and with the "9" setting selected on the rotary switch) after a shortish time as the appliance warms up, the heater should move from low fan speed/2kw output to a higher fan speed/higher gas output combination. A C-3402's higher gas output is 3.4kW, while a C-6002 has two higher outputs - 4kW or 6kW. (Blown-air fan speed is matched to gas-burner output and a C-6002 at maximum output sounds like a jet engine on afterburner.) As the air temperature within the motorhome approaches the setting chosen via the rotary switch, the heater should move progressively to lower fan speeds/gas outputs until, when air temperature and switch settings match, the blown-air fan will shut off. When the heater is running at high fan speed/gas output, it should be possible to cause the fan/gas to turn off and back on by moving the control-panel's room-temperature rotary switch to a low setting (eg "1") and then back up to a high setting (eg. "9").
Although there is no direct link between a C-Series appliance's water-heating operation and air temperature, there is a relationship between a C-Series appliance's blown-air operation and its water-heating capability.
When a C-Series heater is in blown-air mode, air is being forced rapidly through the gaps between the appliance's central heat-exchanger and its outer water jacket. This significantly limits the amount of heat that can transfer from the heat-exchanger to the water within the jacket and, consequently, when the heater is in blown-air mode, water heating will take longer. For a C-6002 appliance, Truma quotes the time taken to raise the water temperature from 15°C to 60°C as around 20 minutes when water-heating-only mode has been chosen, but 80 minutes when the heater is in blown-air + water-heating mode.
I'm not sure if your heater is operating as Truma intended, but it doesn't sound right from what you describe. If it's behaving differently to what it used to, then it's fairly certain something's wrong. Suggest you review Truma's Operating Instructions leaflet to see if you can spot the bit you refer to about water heating and air temperature.
Truma C-Series heaters can be baffling to motorcaravanners, even to those people who have had considerable practical experience of them. In MMM's Interchange section over the years, I've read several questions/answers that related to these appliances and all of them have revealed misconceptions in the questions and factual inaccuracies in the replies.
Posted: 28 July 2009 7:56 PM Subject: RE: truma trauma
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my previous tests were rather haphazard, as the system had drained down, and i put heating and water heating on at the same time. im going to test it out again tomorrow, and will follow your recommendations derek. im not sure whether mine is a c3402 or a c6002 and nowhere in my instructions did it specify or give any sort of clue. the serial no starts c603/e/ but i dont know if that gives any indication to those of you who know about these things.
Posted: 1 August 2009 7:13 PM Subject: RE: truma trauma
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thanks derek for that info. i tested it out again by only putting on the heating, and it came on as it should. i then put it on water only (at the higher setting) and it took about 40 minutes before the orange heating light extinguished. all seems ok.
many thanks to all for your advice, information and tips.