pgAgent service for PostgreSQL does not run
I'm not sure what I did, but I have the service running now. I guess it is a combination of little of everything


Open CMD as administrator
browse to pgagent.exe 


cd C:\Program Files\PostgreSQL\pgAgent\bin 

Remove the pgAgent service (if pgAgent service is installed, but does not work)


pgAgent REMOVE pgAgent

Then I installed the service again. 


pgAgent INSTALL pgAgent -u WindowsUser -p WindowsPassword hostaddr=127.0.0.1 dbname=postgres user=postgres password=postgePassword

(Not sure if the following steps are needed but) Open Windows services
There you can confirm the windows account that runs the service.
open up pgpass.conf in %APPDATA/postgresql and add the line 


127.0.0.1:5432:*:windowsUsername:windowsPassword

add pgpass.conf as system variable PGPASSFILE