D2L and B2L heaters are obsolete and Eberspacher no longer support them. These are very old and gaskets and other parts are probably unobtainable. Sources for some spares at http://www.brick-yard.co.uk/forum/strip-and-fix-eber-d2l-b2l-westy-type-heater_topic61860.html
Photos Tim Claseman taken when he disassembled this faulty B2L.
These heaters were designed for under chassis mounting.
Fan motor with motor control board.
BL2 Spark plug after cleaning.
DL2 would have a glow pin.
Back view of printed circuit board after resoldering. This cleared the original fault but heater was still faulty. The brown wires are the earth or 0 volt power return cables. When the connector became unsoldered fan current could then flow through other components which probably damaged them. No further investigations were done as the owner decided to replace it with a later model.
Faulty Motor control board. Original fault cause is the connector with the brown wires. Here all the six soldered connections to the circuit board have broken. Over time cyclic thermal expansion and contraction plus vibration have cracked the old soldered joints. There is also evidence of corrosion on some connectors.