In my father's 530i (M30), 1988, with climate control and airconditioning, the heating control stopped working.

Because of a malfunctioning blower motor, even after replacing 2 swords (of which we didn't know 100% for sure whether or not they worked), we decided to swap the climate control computer.

After we did that, also the heating control stopped working. Heating was constantly turned on to the max.

We put back the old computer, but the heating kept on going. We already found a way to control the water valves manually, but it would be nice if we could get the climate control running again.

Any idea what might have went wrong when we replaced the computer with one from a 1989 735i? It looked exactly the same but had different numbers on it.

thanks!