Webasto heater model BBW/DBW46 - won't start

[captgrail]

Hi folks,

Just wondering if anyone knows anything about these - mine sat for a few years and will not start now. Looking for some help to troubleshoot what the issue could be. Power on runs 30 secs, then blower starts up (burner activation?) runs 60 seconds and then locks out. I try my best but am not always able to get through these things without a little help or hand holding. Personally I prefer my work in the galley making a scrumptious dinner, 12 volts makes me nervous!
I can't seem to find anyone that KNOWS how to work on them locally. San Fran bay area. I called Sure marine in Seattle but the suggestion was to disconnect it and send it to them. Don't see that happening without a few local attempts while it is still installed! It was working great in the past but unfortunately I was called away from the boat for an extended period of time.

Any ideas or suggestions greatly appreciated. It's cold here!
Thanks in advance for your time.

[glenn.225]

here is a parts site.
DBW 46 - DBW 46

I've worked a bit on various fuel fired heaters and here are some simple things to check.

Since you seem to have power. Does the heater actually fire during start-up (i.e. is there black exhaust or white which is unburned fuel) if it does not fire it could be fuel or igniter.
Is it getting fuel? Is the igniter getting power, is igniter good?
If it is actually firing during start up, it could be the temp switch, (Item 12) this tells the control module that there is flame and it will continue to supply fuel if not it will shut down to prevent flooding. This can be TEMPORALLY jumped for diagnoses.
Another thing is dirty combustion chamber this will need to be disassembled and cleaned.

[glenn.225]

Webasto Manual

http://www.telusplanet.net/public/ga...bw46/bbw46.pdf

[DeepFrz]

Check that you are getting fuel. If it ran before then it is likely that the fuel drained out of the fuel line and the pump isn't able to get the fuel to the burner in time before it shuts down. One way to purge the line would be to disconnect the fuel line at the heater, put it into a jar and supply 12 volts directly to the fuel pump. Run the pump until you get clear fuel, connect the line to the heater and then try firing it up.

Good luck. I know diddly about these heaters but that is what I would do as a first step.

[Scott Berg]

Try running on Kerosene for a bit; it tends to be cleaner and clear up carbon… I run 20l through mine every month.
also, to run it every month for a a cycle (20 min or so) to keep it dry and clean; like so many things (including us) they don't do well sitting still!

[captgrail]

Thanks for all the feedback folks. Here is where I'm at now in this process:

Checking the docs they talk about some relays (K!) that I can't locate. There are two fuses that appear intact - a 5 and a 20 (stamped Potter&Brumfeild) They also talk about startup lights - I don't have those either - the unit works off a themostat.
I've replaced the burner and felt pad and an over heat sensor, verified the fuel pump works, power to the pump works, (BTW, it isn't polarity sensitive which I didn't know) checked the glow plug which is clean and reports .6 ohms uninstalled. I've verified the battery is at 13+ volts. I don't have a replacement flame sensor and Im hoping I can clean it off with some solvent and an emery cloth. The felt pad was pretty much burnt up with a lot of carbon deposit. It sounds much better than it did. I cleaned it out as best as I could with the unit still installed. There was no smoke out the exhaust so I'm not sure the flame is happening.

The only other thing I can think of after the flame sensor is to bleed the fuel line better. I'm not sure pulling the overheat sensor bled the coolant but since the heater is lower than the expansion tank it was streaming out of the top. I guess I will also pull the connectors from the ECU and reset them maybe clean if possible. Any ideas or suggestions of what else can I check? Greatly appreciate any ideas or feedback.

[captgrail]

Hi Glenn, you mentioned that the temp switch can be TEMPORALLY jumped for diagnoses.
Can you please tell me how to do that? Thanks, Captgrail.

[glenn.225]

Most flame sensors in those type of heaters are "normally open" (i.e. will not allow current trough until a certain temp is reached). So basically what you would do is connect a short jumper lead (the alligator clip type) across the two terminals. Now it's been some time since I worked on those and your model may be more sensitive to the resistance in the sensor and common jumper may not work. But the idea is to override the sensor when you know there is an actual flame but you are unsure the sensor is functioning properly. If there is no flame on start up this will not do anything good. WARNING it will cause excessive fuel to be pumped into combustion chamber which could result in fire or worst. So you have to ensure there is actual flame before trying this.
I feel a little guilty about suggesting it, if you are not confident in your abilities in working on a heater I recommend get a pro in.

[captgrail]

Thanks for the reply Glenn and your concern. I definitely don't want to catch my boat on fire to get some temporary heat!. It frustrating to not be able to know if it is getting a flame. I wonder if there is a way to determine that? I have been looking for "a pro" that actually knows these heaters but haven't really found one willing to travel to my location. Best suggestion from a reliable source was to disassemble and ship to Sure Maine in Seattle but that isn't my preference. If I take the thing out something new is going in. Call me crazy but my experience with some local "pros" hasn't worked that well. I could spend lots of money and still not have a fix and then get offered a new one for even more $$. This is why I try to do as much as I can myself and if I do need to get someone at least I can tell if they know what they are talking about. I'll hope some other folks might have some feedback. I may just have to wait until my next haul and get someone thru the yard. I just feel that I am close but might be missing some small detail...

[glenn.225]

captgrail

Hear what you are saying about some pro's, but there are a lot of good people out there. As for it firing you should be able to hear it if your are with in a foot or two. I know in some installs, the heater is buried under a dozen other systems and the controls are 10 feet and two bulkheads away, so you need a second hand. I used to work on armored vehicles (personnel carriers and tanks) and know how difficult somethings are to get to, so it wasn't that of a switch for me to working on boats in regards to "space issues" other things not quite the same.

[captgrail]

I decided to write up a summary of what I've tried and post a few other forums and provide some pics.
---
Webasto DBW46 Heater
This system is installed in a boat. The unit is mounted in the engine
compartment with 4 air vents and expansion tank sitting higher/above.
It hasn't been working for a few years. Thankfully I live in a moderate climate.

Failure mode: Unit powers on via thermostat control, circulation pump
comes on, combustion fan runs but it seems like the dosing pump never
gets activated. The glow plug never gets hot, unit shutsdown 90 seconds
after turn on. (I know this because I took apart the combustion chamber
and removed glow plug after an attempted start)

What I've done so far:
Glow plug - visual inspection looks good, measures .6 ohms resistance
Combustion chamber - cleaned out carbon deposits, replaced felt pad and
burner ring from kit. Seal gasket is in place and looks good.
Flame sensor - cleaned off deposits with mineral spirits
Temperature limiter sensor - replaced from spares (this is the one at the
end, not the one by the flame sensor)
- Checked incoming voltage from battery - 12.6 under draw (pulled down
from 13.7 brand new battery)
- Applied 12 volts direct (on/off) to dosing pump flushed out old fuel
and made sure it worked.
- Checked fuses - there are two 1 is marked "5" the other "20". Neither
look blown but I need to check voltage.

I have already have the service manual. Informative but...

Not sure how I could test that and anything else but I really don't want
to keep throwing expensive parts in to troubleshoot - unless it's a fix.
Any constructive ideas appreciated!

I uploaded a video and some photos mostly for the sound for anyone with a
trained ear: Flickr: ArtStuff1's Photostream
look at the video's comments or photos details for more info.

Thanks in advance for any help or suggestions.