Hello Mark,
Eberspacher is the dogs ballerics of diesel heaters. Usually fitted to upper end motor homes and artic sleeper cab units. Just like a little Boiler, purge fan, ignition unit and spray nozzle. auto ignition and temperature controlled. Run for years apart from jet cleaning. Make sure there is diesel getting to it and the purge fan runs for a few seconds before iginition starts. Fairly quite when running and loads of heat. Exhaust vent must be clear.Might need bleeding.