a side note about Espar Heaters...
I have performed a lot of service on these units and I will say the amount of usage on these is critical to their operation. One should almost always consider "stepping it up" according to size. For example, a vessel of our size , it is recommended (hydronic) M8 or M10 units however, stepping it up to the M12 will ensue this unit is not running 24 hours a day to keep up with the heating demands. One more example, I helped install a unit last fall and by the end of the winter the customer was complaining that it was not working properly. It was making a lot of noise and bellowing white smoke. It had over 5300 hours on it and needed a complete overhaul to remove the carbon build up in the firing chamber. These units should be removed and sent off for service once a season if hours exceed 2500. One more thing that helps these run better is if you cut the fuel with kerosene. The general rule is 10% however, it is not recommended you run your main at this time because some of the lubricating properties of diesel are diluted.
These are DC units and voltages are always critical during operation. Low voltage will also cause carbon build up and failures.
Duane, I agree with Ian your ECU is the likely culprit.
It's all Good