manual mode - Long exposure closing the view finder and producing blank white photo

I have recently brought a DSLR with intervalometer and trying to take a long expxosure photo. But when I set the shutter to 'BULB' mode, F5.6 and ISO AUTO in Manual mode.Now, with all settings at 00:00:00, am getting a nice clear picture. But when I set the LONG to any value and start the timer, my view finder gets closed, the resulting photo is nothing but full white. To check any problem with the intervalometer, disconnected it and set the shutter speed to 30 sec. Even now the photo is nothing but white. How do I get the effect desired?