Installing an Eberspacher heater with an EasyStart Pro controller brings advanced temperature control to your off-grid setup. But what if your heater keeps running -even when your cabin already feels warm?

Installing an Eberspacher heater with an EasyStart Pro controller brings advanced temperature control to your off-grid setup. But what if your heater keeps running -even when your cabin already feels warm? The issue might not be with the heater or the controller itself, but with where the system is measuring the temperature.

A customer recently installed an Airtronic AS3 D2L cabin heater and paired it with the EasyStart Pro controller. Everything powered on correctly, the heater ran smoothly, and there were no fault codes. However, even after the target cabin temperature was clearly reached, the heater kept running.

No overheating. No system error. Just endless heating beyond what was needed.

Through technical support, we guided the user into the EasyStart Pro's workshop menu, which provides deeper configuration options. One critical setting controls which temperature sensor the system uses:

• Heater – Reads temperature at the heater unit (usually installed in enclosed or isolated spaces).
• Control Unit – Uses the Espar EasyStart Pro built in temp sensor, located directly in the controller unit and designed to read ambient air inside the cabin.

In this case, the system was set to “Heater.” That meant it measured temperature near the heater’s body -an area that remained cooler longer than the actual cabin. As a result, the heater never registered that the set temperature had been reached, and it just kept running.

We advised the customer to:

1. Enter the EasyStart Pro’s workshop menu.
2. Locate the temperature sensor setting.
3. Change the source from “Heater” to “Control Unit.”

This change aligned the sensor with the area where the customer actually wanted to regulate comfort. Once adjusted, the heater began cycling properly -shutting off when the cabin reached the desired temperature.

If you're using an Eberspacher external temperature sensor, make sure the system is configured to prioritize that sensor over internal options. A misconfigured sensor hierarchy can cause similar issues with cycling and cabin comfort. Before using an external temperature sensor, in some cases, the heaters' ECU must be reprogrammed using Eberspacher Software - many customers don’t know this and encounter problems.

If you've set the correct sensor but the heater still doesn’t behave as expected:

• Inspect the wiring harness for damage, wear, or corrosion.
• Ensure all connectors are fully and securely plugged in.
• Reset the system by disconnecting it from the main power source
• If the problem persists, contact our tech support and include detailed installation photos for faster diagnostics.

This issue can affect any Eberspacher air heater (12 and 24 Volt systems) paired with an EasyStart Pro controller, including:

• Eberspacher Airtronic AS2 and AS3 Series
• Eberspacher Airtronic D2L, D4L, B4L, D4R
• Eberspacher AM3 Series: D4L, D4R, B4L, D6L, D8L
• Other Espar air heaters that use the Easystart Pro controller

Whether you're using the EasyStart Pro built-in temperature sensor, an external temperature sensor, or encountering an Espar temperature sensor error, the heater’s behavior depends entirely on which sensor is selected.

Sensor location isn’t just a technical setting - it directly affects how your heater cycles. For accurate comfort control, always make sure your system measures temperature in your desired location. Incorrect temperature sensor settings may have less impact in compact spaces like a truck cabin or a crane cabin, but they can lead to noticeable discomfort in larger spaces such as vans or boats, where temperature differences across the space are more significant.