Hello, I bought an old Phaeton with which unfortunately the board of the auxiliary heating is defective. I tested the individual components of the auxiliary heating system successfully with a laboratory power supply. The part number of the old board is 901389A on the Internet I unfortunately did not find a board with identical part number afterwards I picked out a board for the auxiliary heating Thermo Top C (which is installed with me) contacted the seller and shielded him the situation This made sure that this circuit board was also suitable for this purpose. When the circuit board arrived, however, I connected it electrically to the vehicle and wanted to test the individual components by means of actuator diagnostics. The connection was immediately recognized, the test of the combustion air blower incandescent pin etc. was successful except for the control of the circulating pump of the stationary heater V55. Also at the slot of the pump there is no voltage and as said on the laboratory power supply the pump works For this reason I contacted the seller again and he told me that the circuit board is a circuit board for an additional heating not a stationary heating and therefore the pump is not controlled. However, he does not accept a withdrawal of the circuit board. Now the question can be reprogrammed the circuit board and practically care for the control of the pump V55, or I have to buy a new circuit board … If so how do you do it. Attached are a few pictures of the circuit board. Thank you for your help! Mfg Niklas