Autoterm diesel heater broke down in freezing Sweden

How a single unknown problem caused our heater to fail for two months while on the road in Iceland and later on Sweden during the beginning of the winter.

We installed the heater just a few months prior our trip and all the install was done correctly and in accordance with Autoterm air 4D manual. A diesel heater is a very simple technology no matter if its and Autoterm, Webasto, Eberspacher or Carbest. When the installation is done correctly you only have to maintain the heater once a year or every two years, though I’ve seen 10 years old unmaintained Eberpacher looking perfectly fine once opened to service them. So why did ours fail ?

It all started when we realized our heater couldn’t reach it’s max temperature anymore, and then soon after the heater started smoking a little at startup. So far nothing was dramatic and being the the Icelandic highlands we decided to wait before investigating. But we quickly had to do something as the heater started smoking more and more without blowing hot air anymore. In this case the culprit is often a clogged air intake, exhaust or fuel line. After checking all of them I found no problem…

We then started getting error 13 and 78 which indicate failure to start and failure to sustain flame. At this point I had the idea to keep the vehicle diesel cap open as I realized the the breather wasn’t working properly, I could hear the tank sucking air every time i would open to fill the tank. This problem seems recurrent on the Iveco Daily 4x4 as my previous one and my friend’s also do that so I thought this couldn’t be the problem. So i leaned on the hypothesis than the exhaust and particularly the silencer got filled with water too many times during river crossings and the water somehow clogged the fibbers in the silencer.

As we returned to Sweden with the Smyril Line ferry I ordered a new Autoterm exhaust and a rebuild kit and I started dismantling the heater to inspect the combustion chamber and the heat exchanger.

I was surprised with how clogged the heater was, a huge amount of soot built up. At this point I was confident changing the exhaust and cleaning the heater would be enough to fix it !

But then I discovered that the temperature sensor of the heater was disconnected from its terminal ! That must be the reason why the heater kept shutting off since without the temp sensor the heater thought it was not getting hot and so decided to shut down. All exited to have found the reason behind the failure I rebuilt the diesel heater and reinstalled it in the van. And sure enough it fired perfectly and heated us up for the night !

But ! because it would not be an adventure otherwise… the heater started generating too much CO (carbon monoxide) and gradually produced less and less heat, eventually started smoking again and ultimately failed.

At this point I was completely demotivated and couldn’t for the life of me figure the problem. One hypothesis was that the diesel pump failed for some reason.. So I ordered a new one and changed it on the road. At this point the heater started working again and I made sure to keep the diesel tank cap open to let the air in to be sure. A few days passed and we rejoiced that our Autoterm was finally working as the temp dropped below 0°C every night.

Flash forward one week later when I forgot to open the fuel cap and even though I opened it as soon as I realized the heater started producing CO.. and again stopped working a few days later. Now the winter was really coming and with it the snow so I decided to drive to Karlstad to go to an official Autoterm garage. 3H later I arrive for my appointment only to be told that they don’t work with Autoterm since 5years… I still asked the mechanic to look into it and together we came to validate my hypothesis that the bad air breather of the tank was destroying the fuel pumps which then lead to poor fuel / air ratio causing a clog up of the unit. Decided to get this matter resolved I called Autoterm HQ in Latvia and got in contact with their support technician.

I then ordered another fuel pump from VarmaCenter in Stockholm and they shipped it the same day allowing me to pick it up the next day in Karlstad (4h away from Stockholm)

The next day I installed the new pump and started the heater again, still not working argh !! So with the Autoterm Technician on the phone we go to Biltema (and Ikea but for Hardware) to open the heater again and diagnose what is wrong. Once opended of course the heater is clogged up again, so i clean it on the parking lot and check everything with him on the phone. Everything is fine so concluded that the sole problem is the Iveco fuel cap. And finally the heater worked !! we then kept the fuel cap opened until we went to our garage in France to fix it.

BILTEMA parking lot repair with the Starlink mini to have Wi-Fi for the call with the Autoterm Technician 

This was definitely a tough moment as we almost canceled our last two weeks of our trip because of it but we are glad we did not as we got to see the Nothern Lights in Lillehammer during one of our last nights !