Espar Airtronic troubleshooting: internal temp sensor defective


2013 NCV3 2500 170" WB
After a year of running our Espar Airtronic S2 D2L uneventfully, it has suddenly stopped turning on.

Neither the fan mode nor the heat mode work. The Easy Start Pro controller shows these error messages under Diagnostics > "Control Unit"
1. Int. temp sensor defective
2. No Heater

and no error messages under Diagnostics > "Heater"

Has anyone had a similar experience?

My first thought (and the suggestion from the local Espar repair shop) is to try installing an external temperature sensor (~$100) to see if that helps.

I've pulled the electric fuse and reset the system already with no noticable changes.

Thanks for any tips or suggestions!


Active member
Was going to suggest the remote sensor from Le Tonkinois Varnish in the UK as they are a fraction of the price of the Eberspacher ones and are the exact same component. I have one on mine and it works brilliantly.

However, scrolling to the bottom of the page in the link it unfortunately seems that it is not compatible with the D2L

He seems to suggest that it works with a thermostat - so it may be possible to see if you can source a compatible thermostat for less than $100 perhaps?


Active member
Unfortunately, no.

The temp sensor on the D2 is in the unit itself. No idea where the thermostat is on the S2 D2L but I know there isn't anything in the Easystart controller.

*edit* Apologies, I got that wrong. The easy start select doesn't have an integrated temp sensor, but according to the manual the easy start pro does....
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2013 NCV3 2500 170" WB
It turns out that our controller just needed a factory reset. Disconnecting power did not fully reset it, nor did the soft "Reset? Yes/No" option from the settings menu.

To do the factory reset, we had to go to the "workshop mode" on the Easy Start Pro controller by navigating to the clock icon and then holding in the back button. Once inside the workshop mode, there are advanced settings for choosing the temperature sensor (heater or controller) and an option for performing a factory reset.

Hopefully knowing how to get into the workshop mode can help someone else in the future.

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