Pipkim Posted January 6, 2014 Share Posted January 6, 2014 We have a Trumatic Combi 6002EH heater/boiler that is now at least 7 years old. Just recently the unit has developed a “squeaky” sound when the system is shut down but the fan continues to run for a few minutes. It sounds like the fan is either catching on the casing or a bearing has dried up. But it is strange that this only happens on “over run” when the unit is switched off rather than when the actual unit is operating on electric or gas/electric. Has anyone else had a similar experience and if so, what was the cure? Thanks in advance Link to comment Share on other sites More sharing options...
lennyhb Posted January 6, 2014 Share Posted January 6, 2014 Not hear of the problem before. Maybe you only hear it on overrun as the burner has shut down as the noise is masked by the burner noise. Best option would be to replace the fan as you wouldn't want to be caught out on a cold day with no heating. I wish you luck after reading Mike's (onefoot) experience of getting his heater out. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 6, 2014 Share Posted January 6, 2014 I can't explain either why the sound only occurs when the heater is in the overrun (coolng down) phase. Burner-noise masking might apply if the sound only occurred after a period of gas operation. but I assume it also happens after a period of 'silent' 230V running. Has your heater's blown-air fan ever been cleaned? The air that the fan sucks in won't be particularly clean and dust wiil inevitably be deposited in the fan casing and on the fan itself. After 7 years use, if no cleaning has been carried out, there could be a lot of muck on the fan and in the casing and (as you've suggested) the fan may now be touching the casing. There's also the possibility that something more solid has accidentally found its way into the fan casing. I'd try giving the fan and the casing surrounding it as good a clean as you can manage, plus a good vacuum out, and see if that makes any difference. Looking at photos of the model of Knaus motorhome you own, I think the heater is in a wardrobe base or under the foot of a bed, so hopefully access to it won't be too difficult. Link to comment Share on other sites More sharing options...
Pipkim Posted January 6, 2014 Author Share Posted January 6, 2014 Thanks for that Lenny & Derek. The "noise" is more like the "screech" of an unlubricated bearing. As has been said it doesn't happen during normal operation - just when the whole system has been switched off and I assume that it is a cooling fan. I can see on the Truma exploded diagram that there are two fans - one is the "circulating air return line" and the other is the "waste gas discharge". Given that it happens when the gas isn't being used, I assume that it is the circulating air one. The boiler/heater is located under the offside single bed and seems to be quite accessible from the bed or through the garage/locker door. I must confess that it hasn't been serviced since the first year we had the van [2006] so maybe I need my wrists slapped for that! My defence is that we barely use it with the gas - normally we just run it on 240v. Thus I guessed that the gas jets etc. wouldn't need any attention. It is the same with the fridge - rarely run on gas. Phil R Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 6, 2014 Share Posted January 6, 2014 These heaters have 2 fans. One drives air through the heater (the blown-air fan) and the other 'assists' the gas-burner. (In the exploded-view diagram these are, respectively, to the left of "9" and above "10"). The gas-burner fan only runs when the heater is operating on gas. The blown-air fan only runs when blown-air heating has been selected or, for a shortish period, during a 'cooling down' phase after the heater has been switched off. Realiy speaking, there are no maintenance requirements (eg. cleaning of gas jets) for this type of Truma heater, so there's no reason to blame yourself for not having had servicing carried out. There are certain caveats regarding usage (like not completely closing off an air-trunk) and you'll find these in the Operating Instructions leaflet. It's got to be the fan-unit that's causing the noise (as that's all that will be running during the cooling-down phase) and either of your suggestions for the cause sounds reasonable. If you can reach the fan, try spinning it by hand and rocking it to see if there's any play, and see if you can get it to screech. As you observed originally, it's difficult to understand why the noise only occurs when it does. The only thing I can think of is that, when your heater is operating in blown-air mode on 240V, the fan-unit will be spinning relatively slowly, whereas during the cooling-down phase the fan-unit can spin a good deal faster. If play has developed in the fan's motor (or the fan is slightly loose) the increased speed might result in the fan touching the casing. Clutching at straws... Difficult to make a remote diagnosis without hearing the noise. Suggest you initially try cleaning and waggling the fan about. If that does no good, and the noise sounds like something is about to go badly wrong, you'd be wise to ask a motorhome dealer's opinion. You might also try asking the Truma(UK) technicians what they think. Contact details here: http://www.truma.com/uk/en/home/service-center.php Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 7, 2014 Share Posted January 7, 2014 Phil's C-6002EH heater is located beneath a bed and he has said that it "...seems to be quite accessible from the bed or through the garage/locker door". I don't think Phil was in any way surprised or confused by the blown-air fan continuing to run after his heater was switched off. As you advise, it's normal (and it's mentioned in Truma's Operating Instructions). The surprising/confusing thing in this instance, is that the "screeching" noise apparently only occurs during this 'cooling down' phase. I've offered the suggestion that, because Phil normally operates his heater on 240V (when the blown-air fan will be running slowly), the higher fan-speed that occurs during the cooling-down phase might be significant. This is a pure guess, but it should be checkable by operating the heater on gas at a highish heat-output setting when the blown-air fan will be running faster. Information on the Truma safety programme that affected a large number of C-Series heaters is in my 27 November 2013 1:44 PM posting in this forum thread http://www.outandaboutlive.co.uk/forums/Caravans/Caravan-Chat/Truma-Combi-4E-Heater-Problems/32616/ Phil's Knaus motorhome is 2006 vintage, so its heater may well have been affected. As he has owned the vehicle from new, he will probably know whether the recall applied to his heater and, if so, whether the modification was done. As you say, unless he is certain his heater falls outside the recall, or that his heater was modified, he should check with Truma(UK). If it turned out that Phil's heater should have been modified but has slipped through the net, Truma may well authorise the safety-related work to be carried out now free of charge. As the modification involves replacing the heater's top section, blown-air fan-housing and fan/fan-motor as a single entity, carrying out the safety-recall work would undoubtedly cure the "screeching". As you point out, replacing a blown-air fan-unit is not simple. Although it's relatively straightforward to carry out the safety-recall work (provided there's sufficient access), even that needs care as it's possible to make serious mistakes. (I've Truma's instructions for doing this, if anyone wants them.) As you've got various new bits left over after working on your own C-6002EH, can you say, please, what proved to be the reason for the squealing and screeching noises your heater was making? Link to comment Share on other sites More sharing options...
Pipkim Posted January 7, 2014 Author Share Posted January 7, 2014 Thank you all for your comments and suggestions. As Derek has suggested, I have sent an e-mail to Truma technical dept. to see what they have to say. The modification/recall work to the heater was carried out in Sept 2006 by Stowmarket Caravans who commented how nice it was to have good access to the top of the unit for a change! I didn’t realise that the fan casings were changed as well at that time. I have just had a look and can see that there is a lot dust on the fan blades but I couldn’t see that there was any “play” in it that would suggest that it was touching the casing. I probably need to run the system up and then get “up close & personal” with the unit when it is switched off. When we have run it on gas/electric it does sound like a jet engine but there is no screeching at all. I’m not that keen to start pulling the unit to bits and would probably leave it to a professional to resolve the problem, when it is finally diagnosed. It isn’t really a big issue to us [at the moment!] as the heating system works OK – its just an occasional annoyance. Of course, the other option is to change vans!!! A bit drastic I know but we have had so many issues with it in the last year that we have started to lose confidence and will be attending the NEC is Feb looking at alternatives. Thanks again to you all for your comments, Phil R Link to comment Share on other sites More sharing options...
Pipkim Posted January 14, 2014 Author Share Posted January 14, 2014 Response back from Truma:- "I have consulted with our engineer and the fault may be as you surmise either the bushes in the motor are dry and the motor needs replacing or the fan is catching on the housing, your dealer should be able to rectify this for you quite easily." I have got up close to the unit when it is running and the blades aren't catching the casing [otherwise it would be screeching all the time], so it sounds like a new motor is required. Another job to put on the "list" Phil R Link to comment Share on other sites More sharing options...
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