Linking errors using code from my own module

Hello,

I have got an own module with code unrelated to the Unreal ecosystem. Thats also the reason I wanted to seperate it from the other code by putting it in an own module. It compiles well and a module .dll is created. Defining my classes in a header file of the primary module is also working, but as soon as I try to create an instance of that class in a .cpp the linker can not find that class anymore.

1>URiftHUD.cpp.obj : error LNK2019: Verweis auf nicht aufgel÷stes externes Symbol ""public: __cdecl ■■■_slam::InputOutputWrapper::InputOutputWrapper(void)" (??0InputOutputWrapper@■■■_slam@@QEAA@XZ)" in Funktion ""public: __cdecl AURiftHUD::AURiftHUD(class FObjectInitializer const &)" (??0AURiftHUD@@QEAA@AEBVFObjectInitializer@@@Z)".
1>URiftHUD.cpp.obj : error LNK2001: Nicht aufgel÷stes externes Symbol ""private: static class ■■■_slam::InputOutputWrapper * AURiftHUD::ioWrapper" (?ioWrapper@AURiftHUD@@0PEAVInputOutputWrapper@■■■_slam@@EA)".

I can not think of or find a reason for that. What may be the reason my classes are not linked? What am I doing wrong?
I am using 4.7.2 and Windows 7.

Thanks in advance

I externalised my code and build my own lib. My module type is now external.

Type = ModuleType.External;

This should work now.