Hello. I currently have a 1987 300TD station wagon that has been converted to run on vegitable oil for a high school research club. I have been having a problem in that the tachomiter would most of the time not work and the engine would run rough. I was told to replace the overvoltage protection relay but unfortinaly it did not help. I was poking around and the black box to the left of the relay intrigued me. I opened it and there was a circut board. I have taken classes in digital electronics so I regonized that something had gone wrong becasue one of the copper channels was black and sticking out. It looks its one of the wires coming off one of the relays in the circuit. Anyway, with this mentioned, does anyone know how to fix these problems? It looks lik the black box named kickdown is damaged and the overvoltage protection relay is fine. Does anyone here know what to do?

 

Does anyone have any ideas at all? I really need to get this thing fixed. At least does anyone know that the black box marked kickdown behind the relay does? It looks damaged and I want to know what I should do with it.