Webasto Air Top 5000 Problem

[nigel1]

Have a Webasto Air Top 5000 fitted, and it is now failing to operate. The Fault code is not much help, one long flash which only indicates that the unit has failed to ignite after two attempts.
Back in January, during a 700 mile trip it was being a bit eratic, but I thought it was due to low battery voltage. Couple of weeks ago, turned the unit on, it fired up but with a lot of greyish smoke from the exhaust. Let it run for a few minutes like this, then turned it off, wiated a couple of hours, and tried again, this time the exhaust apperared normal.
After that, the unit is now failing to ignite. When I turn it on, there appears to be wisps of white smoke from under the unit, but no ignition. I disconnected the fuel line from the unit, and proved that fuel is getting to the unit.
Is it likely that it just needs to be stripped down and cleaned, or is it going to be more involved. It is only 18 months old.
If any one has stripped down one of these units, any hints and advice would be appreciated

[Engines1]

In our experience the problems associated with the start up and restart after long term sitting are related to fuel, air, and exhaust. The simple checks are to determine system voltage. Take a reading at the heater. Exhaust, make sure there is no blockage and that the exhaust tube is clear of any water or debris. Intake must be free of obstruction. Then it is a simple matter of priming the pump. If the fuel is primed then disconnect the large plug to reset and try again. After sitting a while (Webasto recomends you run the heater once per month) it may take a few trys to restart. Also if you pull the fuse after the first try and fail you can start the clock over.
We have the manuals and such.

[nigel1]

Thanks, checking the exhaust was something I did not get around to, too late now, back at work (at sea) will have to wait until I get home again.
Will pulling the fuse have the same effect as disconnecting the wiring harness to make the reset??
If after your suggestions it still wont start, I will strip down and check the glow plug. I have downloaded the service manual for the air top 5000 and it seems pretty straight forward

[Engines1]

Pulling the fuse is supposed to work but I find myself pulling the large harness plug from the heater while power is on. Also when you do your next check, get the exact model and serial because I believe there is a firmware upgrade that may help.

Tim

[nigel1]

Hi Tim,
Thanks for the information on the firmware upgrade, I'll get the info to Webasto and see if it is applicable to my unit

[GeoPowers]

Hi nigel1,

I have gone through the exact same thing in my Webasto, although I have a 90S hydronic unit. I also had the fail to fire fault code, wispy white smoke, and heavy smoke when it did fire up. The fact that you can make it work intermittently by trying to shut it on and off probably means it needs a good cleaning to get rid of all the carbon build-up, especially if it hasn't had one in 18 months. The white smoke is from all the diesel getting pumped into the burner unit of your heater on start-up, and then not firing up. When it does finally fire up, it gets the same amount of air, but a lot more fuel than designed for, making your dockside neighbors wonder if everything is okay! If you shut it on or off enough without it firing up, the unit can even "dump" excess fuel that you will see in your bilge. My service tech here said that if possible, it may be best to unhook the fuel line coming into the heater and point it into a cup, letting the unit fire up with the diesel that is already in the burner unit. If it has too much fuel in the burner, this can also give it difficulty to start. If you do this, you will have to re-prime the fuel line. For me, a servicing/cleaning did not fix the problem. I took my unit to a Webasto dealer for a good once over, and it bench tested with no problems. I reinstalled it and my unit worked for about a week, then started working on and off, and stopped working all together. After two more trips to the shop, we finally determined that the cause of the problem was a faulty burner unit. The service tech won our bet- I thought it would be the flame sensor that was faulty. ( I wish I would have just went with his opinion, that would have saved me a install/removal of the unit, and some $$ on the new flame sensor!) Anyway, a new burner fixed the problem for us. Hopefully for you it just needs a good cleaning. If you have a copy of the service manual, it should be clear on how to disassemble the burner unit from the control unit and give all the combustion areas a good cleaning. If you don't have the service manual, PM me and I can give you a website to get it free.

Good luck!

Frank

[nigel1]

Thanks Frank,

did find diesel in the combustion air intake hose. Will strip down and de-coke wjen next on the boat, should only be the cost of a gasket kit. (I hope)
I have downloaded a copy of the service manual, and the strip down looks easy enough once the heater is out of the locker

[nigel1]

Heater fixed, found the exhaust flooded with condensate and diesel, and the burner unit heavily coked. Good clean and its back in operation.
I'll have to have a think on the exhaust set up, the root of the problem would most likely be due to condensation building up in the exhaust, which due to the placement of the heater, cannot drain naturally. Ideally a drain fitted in the exhaust would help, but the exhaust pipe is in the same space as the air intake, so dont think that would work. Back to the drawing board