Here is a quote from a helpful web page Controllers 1 and Remote sensor
They are boat people but the heaters are the same.
Controller confusion
Eberspacher' s complete lack of consistency in naming controllers causes much confusion.
Eberspacher use 'Rheostat', 'Modulator' and 'Controller' to describe the same basic unit, ie a device with the on / off switch and a set desired temperature function.
Making things more complicated there is also a separate type of controller inside or close to the heater that is the 'brains' of the unit, ECU Electronic Control Unit on early heaters, ICU Integrated Control Unit on later versions, we always refer to these as ECU on these webpages.
A major difficulty buying second hand controllers is separating modern types from those with a thermostat which will only work with older models like the D1L etc. Eberspacher information on older controllers is not available so identifying those can be impossible. Some controllers are made by vehicle manufacturers.
Most controllers not listed here will probably be thermostat types, not suited to D#LC, D#LCC, Airtronic.
Further problems are caused by many users thinking modern controllers are like conventional central heating thermostats. Except for a few models Eberspacher air heater controllers do not measure the ambient temperature, they just send a signal to the Eberspacher basically saying 'The control is set at this temperature’. The heater measures the actual air temperature at its air inlet and adjusts the heat output to match the user controller setting. If the heater is close by this can work ok but if it is farther away or in a locker the temperature there can be greatly different. It fails completely when the heater circulates fresh air. The sensor then thinks that the temperature of the outside air is the ambient temperature and of course that does not change as the heated area warms up. Even worse if the outside temperature drops below its lowest setting, usually between + 5 and + 10°C, the Eberspacher can automatically switch to maximum heat output, completely ignoring the temperature controller setting. The solution to both of these is to fit a remote temperature sensor.
They are boat people but the heaters are the same.
Controller confusion
Eberspacher' s complete lack of consistency in naming controllers causes much confusion.
Eberspacher use 'Rheostat', 'Modulator' and 'Controller' to describe the same basic unit, ie a device with the on / off switch and a set desired temperature function.
Making things more complicated there is also a separate type of controller inside or close to the heater that is the 'brains' of the unit, ECU Electronic Control Unit on early heaters, ICU Integrated Control Unit on later versions, we always refer to these as ECU on these webpages.
A major difficulty buying second hand controllers is separating modern types from those with a thermostat which will only work with older models like the D1L etc. Eberspacher information on older controllers is not available so identifying those can be impossible. Some controllers are made by vehicle manufacturers.
Most controllers not listed here will probably be thermostat types, not suited to D#LC, D#LCC, Airtronic.
Further problems are caused by many users thinking modern controllers are like conventional central heating thermostats. Except for a few models Eberspacher air heater controllers do not measure the ambient temperature, they just send a signal to the Eberspacher basically saying 'The control is set at this temperature’. The heater measures the actual air temperature at its air inlet and adjusts the heat output to match the user controller setting. If the heater is close by this can work ok but if it is farther away or in a locker the temperature there can be greatly different. It fails completely when the heater circulates fresh air. The sensor then thinks that the temperature of the outside air is the ambient temperature and of course that does not change as the heated area warms up. Even worse if the outside temperature drops below its lowest setting, usually between + 5 and + 10°C, the Eberspacher can automatically switch to maximum heat output, completely ignoring the temperature controller setting. The solution to both of these is to fit a remote temperature sensor.
