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Webasto Diesel Warm Air Heater


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On Happy Jax II we have a Webasto heating system, I believe it to be a common unit as fitted to many hire craft. It has proved to be very reliable and fires up first time every time. However, when it gets up to temperature and shuts down, it starts to belch out grey/black smoke from the exhaust for approx 30 seconds, then fires up again and all clears until it reaches temperature and the smoke starts again. If anyone has any experience or advice on these units it would be very much appreciated.

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Pretty much par for the course Col, after a year or so of hard use the vaporizer gauze and plug gets a bit caked and takes a little longer to get the fuel burning cleanly and a bit of smoke is the result (sometimes more than just a little). A decoke would probably not go amiss come summer as contrary to popular belief they are not fit and forget.

One point though, they should not actually shut down when the temperature target is reached but rather reduce output and maintain the temperature. Run it hard next time you are down, full heat and open a hatch if need be. If you do that from time to time it will help.

BTW, what model and how long has it ben fitted?

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Thanks very much for the advice David.

Not sure of the model, but have to assume it was installed when the boat was built in 1998. I would imagine the smoke starts when it reduces output after the target temperature has been reached. We was up on the boat last week for New Year and must say it was run very hard then. Is it a difficult task to decoke or should it be left to the specialists?

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Depends on your level of DIY skill Col, that’s why I asked about the model so I could point you to a manual then you could read and decide for yourself if you fancied a go.

Apart from the electronic boxes and relays if external, or the internal PCB or control box if a later model they are quite industrial and easy to work on with a little care, though very messy to decoke so don’t do it in the kitchen or you’ll have SWMBO on your case.

Next time you are on the boat have a look for the makers plate which will have model, serial and probably year of make then we can sort you out a workshop manual and parts list.

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  • 3 weeks later...

I pulled the heater out this weekend and stripped down to give a decoke, as you say David, it's not a difficult task. I must say it was very coked. I rebuilt it up and tested. As usual it fired up first time, well after I turned the Diesel stopcock back on. :oops:

But when the burner cuts off it still belches out smoke from the exhaust. Could it be the burner unit?

As requested gents, I tried to get model numbers/type of unit but could not see any. I have taken several photos, could anyone advise on model type and where I could get spare parts.

The boat was built in 1998 and I assume it is the original unit. Any help would very much be appreciated.

post-167-136713479744_thumb.jpg

post-167-136713479766_thumb.jpg

post-167-136713480025_thumb.jpg

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Looks like an AT 3500 or 5000 from the pictures, probably quite a bit later unit than the build year of your boat. It may benefit from a new burner tube if the evaporator gauze is badly burned and clogged; the gauze is one of the most difficult if not impossible bits to clean completely. A manual and parts list can be downloaded from the Webasto site for no charge.

http://www.techwebasto.com/marine_blueheat.htm

One thing that arises from the pictures is the exhaust; it rises quite sharply from the unit instead of continuing downward and in such circumstances needs a condensation drain at the lowest point. Parts can be obtained from many places on ebay or if you want to buy locally then JPC are good. You may well want to get them to set the CO2 level as well, this may reduce the fuel air ratio to a level where the smoke reduces.

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Well spotted Jimbo, I missed that :oops: any bad restriction in the combustion intake will increase the fuel to air ratio and possibly cause poor / non starting and smoke, though it is likely that it would smoke permenantly if that is the cause.

Another thought, when you say decoke, did you soak the burner tube in caustic soda to get rid of the hard carbon deposits caked in the gauze or just get rid of the loose stuff in the heat exchanger (more like soot than baked carbon) and did you blow the exhaust through to get rid of any soot and or condensates in there?

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Hi Jimbo/David

I note your point regarding the intake hose, and I must say it does looked kinked in the photos. I have checked this and it is not restricted. When the heater is running it is fine with no smoke at all. When the burner stops, i.e you hear the burner roar cease, that is when the smoke starts. When I stripped the unit, the burner tube and complete heat chamber was full of coke. I decoked using carb cleaner. The actual burner itself, I was cautious with and don't think this was cleaned as well it could be. Problem being, never seeing one before I am not sure what it should look like.

cheersbar

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Col, the evaporator gauze (at the bottom of the burner tube surrounding the glow pin) should look like a disc of metal with tiny perforations, a bit like a small round teabag. You did right not to poke at it too much but your last post makes me think that it probably needed a good soak in Caustic. Carb cleaner would do the inner walls of the exchanger very nicely but the gauze needs something a bit more aggressive, though not mechanical scraping. :grin:

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Guest chriscraft

hi

something to consider,if your unit isn,t smoking when on load,and smokes on temperature cut out,you could have a problem with the dosing pump,If this isn,t shutting the diesek off cleanly,there will be a drible of diesel into the hot combustion chamber,causing carbon to build up,and smoke(incomplete combustion),in extreme cases the exhaust would become sticky,eventualy bunging the whole thing up,may be worth checking this unit,if it,s a servicable item,it may have a bit of floxam under the seat

regards trev

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  • 4 weeks later...

Interesting article I have paraphrased, it does allude to a canal boat and some of the so called "Red" available on the canals is little better than heating oil, but interesting nonetheless.

In an attempt to ascertain the nature of the problem, Webasto UK visited a boat in December, 2007, and January, 2008, and carried out an experiment for a period of just over a month. As opposed to the normal red diesel that had been used they asked , for the duration of this experiment, to run the heater on white road diesel only. The heater appeared to work perfectly when run on this white diesel but when connected back up to red diesel began, over a period of time, to fail again in its ability to restart itself after its initial 30-40 minute cycle. On conclusion of the experiment, Webasto report on the heater which concluded that … “The most probable cause for the high build up of carbon and reduced burner life is due to an excessive presence of sulphur and/or other unknown properties within the fuel and/or fuel tank, and is not in any way related to a Webasto product or installation issueâ€.

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I an beginning to agree with Webasto re High Sulphur content fuel, based on my experience.

My father in law was a Logistics Manager for one of the countries bigger Haulier's with almost 300 vehicles under his control including the maintenance budget. I asked him were the 'Night Heaters' (as they are known on Lorry's) as much of a problem as on boats, his answer was they virtually never had a problem with them.

Seems to me that fuel is the key culprit and it does make one wonder about fitting a separate fuel tank and run your Webo with White diesel. Trouble is I might not be able to claim the 40% rebate for my heating :naughty:

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