We often say that our Webasto air heater is one of the best feature we added to our campervan conversion… until it stopped working… Unfortunately, Webasto / Espar are prone to carbon buildup if some parameters are not right. What is carbon buildup (also know as soot, coking, carbon debris)? It’s evil! It takes root in the burner insert and slowly accumulates under the form of hard black/grey ashes:
This hard carbon deposit clogs the stainless steel “sponge” found in the burner insert; the role of this sponge is to diffuse the fuel and mix it with air. The hard carbon also builds its way up just outside this sponge, messing up the air flow in the burner and speeding up the carbon debris accumulation.
If the Webasto heater can’t start and/or shut down prematurely, it’s probably a symptom of hard carbon buildup. We had these symptoms after only 200 hours of using our Webasto Air Top 2000STC (we have the gasoline model).
Carbon buildup CANNOT be removed/cleaned from the burner insert! Because the stainless-steel sponge is so fine, it’s impossible to remove the carbon from there. An attempt to clean it will give the impression that it solved the issue, but carbon buildup will come back after a short period. This is what TechWebasto told us and we believe it’s true, because our burner insert was cleaned and the symptoms came back after about 75-100 hours…
Well, cleaning the burner insert didn’t work. It looks like we have to replace the burner insert and this is the topic of this article! But first, we would like to eliminate the source of the issue… what causes hard carbon formation in the first place?? We’re no expert, but here is the information we gathered during our saga.
CAUSES OF HARD CARBON FORMATION:
- Webasto Gasoline models are more prone to carbon buildup than Diesel models! This is counter-intuitive, but this is what we were told by TechWebasto (quote: “because gasoline is less energy-dense than diesel“) AND we found SO MANY people with issues that we believe it’s true.
- A rich fuel/air ratio (too much fuel) will lead to carbon buildup. There is less oxygen at higher elevation, so the mix get too rich in fuel. If used frequently at more than 5000 feet, the unit should be adjusted for high-altitude usage (faroutride.com/webasto-espar-high-altitudes/). In fact, we will go ahead and say that the gasoline models should be adjusted for high altitude out-of-the-box, whatever the altitude you will be using the heater.
- Air flow restriction in the intake/exhaust pipe. The total length of the intake + exhaust pipe should be less than 5 meters. If using an silencer, the length is reduced to 2 meters! Condensation accumulation in the exhaust pipe will also create air flow restriction, so a 3/16” drain hole MUST be drilled at each low point in the exhaust routing (see our Installation Article).
- Short cycle time. If the Webasto is fired-up, it should be run for no less than 20-30 minutes.
- Running on LOW for extended period of time and cycling ON/OFF.
Now that we have a better understanding of the carbon buildup causes, here is our plan.
INSTALLATION MODS TO PREVENT CARBON BUILDUP:
- Replace the burner insert with a new one (keep reading for more!)
- Perform the following to reduce the chance of carbon buildup:
- Remove the exhaust silencer.
- Drill drain holes at low points of the exhaust routing.
- Adjust the Webasto heater for high-altitude usage (we would do this even we didn’t plan on going to high altitudes). This is still O.K. to use it at sea level; the downside is that we can lose around 3-4% BTU, but we rather live with it than have carbon buildup again!
OPERATION MODS TO PREVENT CARBON BUILDUP:
- Run the heater at HIGH for about 10 minutes before turning it off, every time.
- Don’t let the heater run at LOW for more than a few hours. And NEVER let it cycles ON/OFF. To do so, we use the Timer and Program features of the MultiControl HD (Buy on Amazon). For example, we run the heater at HIGH when we go to bed and set the Timer to turn it off an hour or so later (the time totally depends on the temperature outside). Then we set the heater to start early in the morning using the Program feature. That prevents the heater from running on LOW and cycling all night.
Are we sure these will solve the carbon buildup problem? NO! But we like our heater so much (when it works) that we’re willing to give it a try!
- October 2017: We performed the mods listed above.
- March 2018: The Webasto worked fine all winter 🙂 No maintenance performed.
- February 2019: Still running fine, no issues! No maintenance performed.
- September 2020: Still running fine! No maintenance performed.
- September 2021: Still running fine, but we noticed it takes a little more time to ignite. After 4 years without performing any maintenance, we decided to replace the burner insert as preventive maintenance for our peace of mind (winter is coming!). The amount of carbon is actually not that bad for 4 year without any maintenance:
Order these from a local Webasto dealer (Webasto Dealer Locator) or from Amazon:
- A new burner insert
- A new set of gasket (Do NOT re-use the same gasket!)
- Gasoline/Diesel: Part number 82302A (amzn.to/340RHfx)
- Webasto Air Top 2000 STC Workshop Manual
- Webasto Air Top 2000 ST Workshop Manual
- This video made by TechWebasto: (this video is pretty much all you need, MAKE SURE TO WATCH IT)
Let’s do this!
First things first, get that faulty Webasto heater out of the van. Since we installed it ourselves, we figured how to remove it: https://faroutride.com/air-heater-installation/
We want to thank our friends Chuck and Sam for hosting at their place during that process, that helped A LOT!! Sam is a young talented photographer about to build and move into a van, make sure to check him out!!
We now remove the plastic outer casing. No tools needed, it’s all clipped-on:
We then use a flat head screwdriver to spread the retaining clip of the fan:
Next, we disconnect all the connectors from the control module:
And we remove the control module. There are 3 screws to remove:
The control module can then be removed:
Next, we remove the combustion fan module. There are 5 screws to remove:
The combustion fan module can now be removed. Discard the gasket:
We’re getting close to the burner insert. Remove these 4 screws and the 3 rubber grommets:
Now, pay attention. The complete combustion chamber assembly wants to come off, but it won’t work because the fuel pipe (which is attached to the burner insert) won’t clear the cutout. You need to separate the burner insert from the rest of the combustion chamber assembly. They are slightly sticked together, use a little bit of force or use a flat head screwdriver to pry them apart. Here is a picture showing how they come apart (the picture was shot later in the process):
Note that there is a gasket between the burner insert and the combustion chamber, discard it.
Here is the removed burner insert:
There is definitely carbon buildup in there:
The flame monitor (gasoline models only!) and the glow pin are still attached to the old burner insert. Remove them and keep them for re-installation in the new burner insert:
Here is a sneak peek inside:
There is soot in the form of fine black powder. We cleaned it using a toothbrush and White Gas (Camp Fuel). (the manual says to use benzine, but we’re not sure where to find that?!):
O.K., it’s time to re-assemble everything using the new burner insert and the new gaskets. Just do everything in the opposite order! Be very careful not to bend the fuel pipe of the new burner insert and be careful to replace the electrical wire at the exact same place they were. Just look at the pictures above as reference.
We’re done with the burner insert replacement!
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