Periodic Webasto Shutdown

Our webasto heater will run for 4 to 12 hours then the "heater on" light will go off and the burrner will quit working. Turn off the "central heat control" button and give it 10 minutes, and it will restart and run for hours. I have no experience with these heaters. If there is a way to trouble shoot this in the park that would be great. if not, we will cut the stay short and head for home ... expected to be 31 degrees in the coming days so the heat pumps are really not an option. Maybe fuel / filter issue ... or control of some kind?

Thanks as always!

The cards in the ECC should be slots 17 and 18. You might try reseating them and the connectors on the Webasto controller. Before doing that, is there a call for heat? Maybe, the heat demands have been met and the heater is turning off as it should.

Thanks Gil. If it quits raining, I can look at the boards. In the mean time, as far as I can tell, the HVAC t-stat controls the zone fans (on or off) and the webasto appears to fire separate from that presumably based on loop temperature. The "heater on" light will remain illuminated even when the webasto cycles off normally. But when that light goes out, the webasto remains out of service until I turn it off for a few minutes. I don't have my diagrams with me but based on the one you sent earlier today, that light is triggered from the webasto controller so I would assume that something takes it off line then the signal is gone and the light turns off.

"Maybe, the heat demands have been met and the heater is turning off as it should". NO, I dont think so. When the heater on light goes out and the webasto shuts down, the t-stat is calling for heat in one or more zones and the fans are running ... but obviously blowing cold air.

I had a similar issue and it was the overheat on the Webasto. The controller had failed and would allow the unit to run until it reached the manual overheat reset temp. If you have the engine heat loop open on the Webasto you can check by turning the engine key to on and see what the coolant temp is. If the temp is over 180 I would look at the overheating. The fix was simple as it just required the controller to be replaced.

Thanks James. That could be it. Last night, I raised the room t-stat temperatures a couple of degrees, and turned the fans to high and also brought in the rear bedroom zone. The webasto has been on since mid day yesterday without going off line. If it was an over heat issue, maybe the additional load and the colder outdoor temps kept it just under the reset temp?

I also wonder about how the single Duo-Therm t-stat talks to the webasto / CC control system. I have three roof tops that are all controlled off of the single t-stat. Zone 1 and Zone 3 have furnace options. Until last night, zone 1 was set to furnace and zone 3 remained set to heat pump but at a low temp setting. With the zone 1 furnace on for the living and galley areas, there was no call for the heat pump in the bedroom so it never ran. But I was wondering if not having both zones set to furnace if there could be the occasional mis communication between the t-stat and the webasto/CC control that shut it down. Last night, with the bedroom zone 3 on furnace we had no issues.

When we get home I can check out the controller. Thanks again for your input.

I don't think what you did would "mask" the overheating issue. When mine was having the issue the outside temp was about 5. The Webasto has a large BTU burner and should only have to run for around 10 minutes to get the coolant hot and shutoff. When it is overheating the coolant the unit will just kept running until it overheats and shutdown. On mine it took about 45-60 of burn time to overheat. The problem with the Webasto setup in many of the coaches is the on/off switch for them turns the burner on and it is preset to keep the coolant at 165 (I think). The on/off has no relation to the coach needing heat or not. Then there is separate control of the indoor heat exchange/blower units. There is no relation between the 2 other than the indoor units do not get 12V power unless the on/off switch for the Webasto is on.

I would think since you have a single t-stat it would know that Zone 1 wants the furnace on, however I could see something going wrong in the t-stat and Zone 3 shutting the furnace (Webasto) off. The way the t-stat works with the Webasto is the t-stat sends an on signal to the Webasto on the remote control input. Once the Webasto is on it only keeps the coolant hot and circulating. Then the indoor units turn on and off based on the set point inside. If you have a separate on/off switch for the Webasto then the t-stat only controls the indoor units by turning them on and off based on the set point and never actually communicates to the Webasto. When I first converted my coach to roof top heat pump units the CCC2 t-stat of Dometic only controlled the indoor blowers, but I later rewired so it can turn the Webasto on and off without the separate switch. Now, through automation, I have mine turn on the Webasto and then 5 minutes later it turns on the indoor blowers to prevent cold air from blowing the first few minutes while the Webasto heats up.

James, I agree with your thoughts and they appear to be consistent with the way the system is operating. I am not sure though how the country coach electronics in between the webasto and the t-stat might or might not affect this though. We will see if it runs all night again this evening.

BTW, I do not want to be anywhere near 5 deg !!!

Mark, the thermostats do control the Webasto and the coolant flow control valves for the heat exchanger in that zone. If a heat exchanger zone or hot water heater doesn't call for heat the Webasto isn't going to fire. At least that's how I recall the functions.

Here is my suggestion, I had the 5 button Dometic thermostat. Your doing it right if the Webasto is running. The issue of not shutting down could be the thermostat in one of the zones is calling for heat and not sending the signal that the set point has been reached and shut down. Try this, put one zone on furnace mode at the thermostat. Let the webasto come on and run a few minutes, then go to the thermostat and turn that zone off, then turn the next zone on and let run for a while then turn that zone off and let the heater shut down then try the third zone and let the heater run. Hopefully if one to the three zones keep running then it could be the thermostat.

Another thing is my coach had three temp sensors in the coach in the living room the galley and the bedroom, small round black disk with slits cut in it. These are the zone temp sensors, one of them could be bad.
If the heater is coming on something is calling for heat. The thermostat in furnace mode, the hot water heaters calling for heat or the engine block is calling for heat if you have that zone on and its cold enough out side.

If none of this works then I suggest a malfunctioning of the controller on the Webasto.
The Webasto has two thermostats on the heater under the black cover, one for operating temp, around 160 or 170 and an over temp sensor that will shut the heater down.

After setting both zones 1 and 3 to furnace, the webasto ran for around a day and a half and I was about to call it a control issue. But then it quit. I got it to run another hour or so and that it would not fire again. So good news is that it is no longer intermittent and should make trouble shooting easier!

As for the operation, it would appear that mine operates closer to James description. The webasto would fire on and off during the day with or without heat exchangers running. So I assume that it was operating stand alone with the internal loop temperature control. The "heater on" light seems to be a system status indicator not an indicator that the burner is firing. It would remain illuminated even when the burner met set point and shut down.

The heat exchanger button enables the heat exchanger fans which are then brought on and off via the two furnace zones on the thermostat. Again seemingly independent of when the webasto was firing.

Now that I am back home, I will open the unit up and check the condition of the igniter etc. If necessary, I guess I can buy the diagnostic tool.

On a side note, this trip was a character builder. Not only did the webasto finally give up the ghost, but a couple of miles from the park on the way home, the transmission locked into first gear. Prevost Pass was awesome as usual and we figure it is a speed sensor on the transmission. So had the bus towed to Prevost Forth Worth (its home away from home) and they are looking at it today. Damn it is expensive to tow one of these. If that was not enough, the toe jeep developed a serious mis fire making it almost un-drivable. One of my boys came and saved the day, so I am working on it now.

Thanks again, I will keep you posted.

On my 99 CC the Webasto light that turns red should go out when the unit is not running. Stays unlit.
The only calls for heat are the thing I mentioned before, the thermostat for any of the two zones, the engine heat loop, the hot water heaters or the bay heat coils in the plumbing bay.
If your Webasto light is staying light all the time even if you have turned off the central heat button, there is a problem with the card in the ECC cabinet.

I am finally working on the webasto. I have two identical small fuel filters in series. I did not see anything about two filters being required in the manual. Is this something that is required or has someone modified this over time?

Since they are the same, I am not sure what the advantage is unless someone is worried that one of them could have a catastrophic failure and the second would continue to protect the pump and nozzle. But this would only be the case if the first one failed not the second.

In addition, two in series puts more suction head on the pump making it harder to get fuel.

Am I missing something?

My 99 had the two white plastic filters.
I took them out an installed the smaller Racor filter next to the bigger Racor for the engine.
A suggestion is to check your fuel lines to the filters and from the fuel tank, mine were dry rotting and cracking which can suck air into the line. Those lines get very brittle over time.

Thanks Buddy. For the time being, I am thinking of using one of the plastic filters similar to the Webasto diagrams.

What filter size (microns) did you decide on for yours?

Just a heads up... the small plastic fuel filter on our Webasto was rated for gasoline, not diesel. There is a similar filter for diesel but it is not as widespread available. I ended up ordering it on line.

For my application, I used WIX 33972. Here is the product description that mentions the diesel/gas application:

PARTS DETAIL Principal Application: Plastic Universal In-line fuel filter w/ 5/16 lines - can be used w/ gasoline or diesel fuel (33002 only to be used w/ gas) Style: Fuel (Complete In-Line) Filter Service: Fuel Type: Full Flow Media: Plastic Mesh Height: 3.636 Outer Diameter Top: 1.828 Outer Diameter Bottom: Closed Burst Pressure-PSI: 58 Max Flow Rate: 1 GPM Nominal Micron Rating: 50

I think it was a Racor (Parker Ind) 2010 with a 2 micron filter.

I had a similar issue with my Webasto shutting down in the TX cold snap once the temps got below 15°. Just on a hunch put a gallon of diesel conditioner in the tank which was full at 200 gallons and ran the main engine for two hours. It appeared to heat up the fuel, if that was the issue, and when I fired back up the Webasto worked like a charm since. It ran a full week after the shutting down episodes. Didn’t think it was cold enough to cause a gelling issue but the conditioner seemed to work and maybe that fuel line to the Webasto is so thin it was struggling to get enough fuel? I also notice now it appears the Webasto is smoking less now and burning cleaner? Will get in for service now it’s warmer either way.