Three year old rheem gas furnace kept blowing 3amp fuses when calling for heat, fan and a/c work fine.I attempted to troubleshoot by disconnecting components and running it.It seemed that I isolated problem to control board.After reading many posts online about similar problems I decided to install new control board.$160.00 later I'm still blowing fuses.Any ideas would be appreciated.

Check for worn or shorted wiring. Check all heating components i.e. limits,valves,etc for internal shorts to ground. Had one with a disc limit that you have to take the limit off the furnace before you could see the short circuit. It is a time burner to check it all.