If your Espar or Eberspächer heater shuts off shortly after startup and displays fault code P000115, you’re not alone. This issue is more common than you'd think. Many air heater models can shut off if there are issues with hot air flow.

If your Espar or Eberspächer heater shuts off shortly after startup and displays fault code P000115, you’re not alone. This issue is more common than you'd think. Many air heater models can shut off if there are issues with hot air flow.

In this blog, we’ll share a real-world case, break down the cause, and offer simple tips to prevent your heater from shutting off. If you're searching for help with the Espar overheat code or dealing with Espar bunk heater overheating, you're in the right place.

A customer recently contacted us after installing a new Eberspächer Airtronic AM3 D4L with an EasyStart Pro controller. The heater had proper power from the vehicle’s main battery, and the fuel pump was ticking as expected. Still, the unit shut off just moments after trying to start. The customer also noted a smell similar to burning plastic.

The heater's diagnostic system had stored one fault: P000115. This error code usually means the heater is overheating. It detects a temperature spike that goes beyond safe limits and shuts down automatically to protect itself.

After checking the customer’s installation, we spotted the problem - a very sharp bend in the hot air ducting. The problem with this bend was that it was very sharp and located too close to the heater’s outlet. This bend created airflow restriction, trapping hot air inside the unit and triggering an overheat shutdown.

Sometimes bends in ducting are unavoidable in tight spaces. However, they should never be placed immediately after the heater outlet. Key contributing factors to overheating include:

• Sharp ducting bends close to the heater
• Improper outlet hoods (e.g., 90-degree aftermarket versions)
• Restricted or kinked exhaust routing
• Incorrect ducting configuration and layout in longer setups
• Heater installed without adequate space for air circulation.

Each of these factors limits airflow or exhaust gas dispersion, causing the heater's internal temperature to rise rapidly.

We’ve found that many customers facing this issue had installed their heaters in very confined spaces. Most of them had small boats or compact vans that did not have enough room for a proper ducting layout. Brand does not matter either - this can happen to both Eberspacher and Webasto heaters.

It’s important to check the space requirements for your chosen cabin air heater and hot air ducting in advance. If space is limited, consider using a smaller heater model, as long as it still meets your heating needs. Installing two smaller separate air heaters can also be an option in some cases.

To prevent P000115 errors and similar shutdowns:

• Keep ducting bends gentle and as far from the heater outlet as possible
• Use only the original outlet hoods provided with the heater kit
• Ensure exhaust pipes are free of sharp bends or clogs and do not exceed the length limits
• Always follow the official installation guide for your heater model

These simple precautions can prevent serious issues and significantly extend the life of your heater.

While this case involved the Eberspacher AM3 D4L, overheating due to duct or exhaust layout can impact many models, including:

• Espar / Eberspächer: Airtronic D2L, D4L, B4L, D4R, AS3 D2L, AS3 B2L, AM3 D4L, D4R, B4L etc
• Webasto: air heater like Air Top 2000 S STC, EVO 40, EVO 55

Basically, any air heater can have this issue if there is a problem with the ducting or exhaust layout.

Installing a diesel air heater isn’t rocket science, but it does demand attention to airflow design. Fault code P000115 is your heater’s way of saying, "I’m overheating - fix my airflow."

If your heater is shutting off or showing similar symptoms, start by checking your ducting and exhaust layout. And if you’re unsure, reach out to Heatso Support.