I just spent a few minutes searching for what you have and didnt find much, this site, looks to sell controllers similar to what you have, as I got a few hits from the search engine for it. Take a look at this link and see if you recognize the controller.
http://www.ripmax.com/7index.asp?Ite...tegory=060-050
Also, you mentioned that this controller is rated for "8-24 cells" (which equals 9.6v - 28.8v) ..... if you only have a 6 volt battery set-up, then the controller could be going into a failsafe mode, as it "sees" less voltage than what it is designed to operate, or a dead battery condition. Most speed controllers have this feature built in and is set from the factory, although you can change it after you program it (if you knew how)
If you could post a close up picture of the controller, it may help us to atleast identify it and point you in the right direction.
~James