Hi, I have the same exact problem with my KF-50WE620. I tried the same thing that you did; I powered up two of the 3 fans and they function. Where did you locate the connection for the 3rd fan (the one that sits under the optics block)? I do however think that the 3rd fan likely functions. When I power up the TV the lamp comes on for a few seconds, then the set powers down with the 4 flash fan issue. I think (tough to tell for sure) that my fan under the optics block may just start to rotate for about 2 seconds and then everything powers down. The power supply board is the "G" borad which in turn sends the 11V to the "A" board. The "A" board controls the fans. Unfortunately the "A" board is tough to work on but it does have 3 ICs for fan control: Fan 1 is IC8003, Fan 2 is IC8005 and Fan 3 is IC8006. I'm trying to figure out what Sony calls fan 1 , fan 2 and fan 3. It looks like one power line feeds all three. I've been trying to get any info on a possible thermal fuse or any information on parts to test and troubleshoot but there's not much out there. I cleaned the outer fan and will now try to clean the smaller fan that sits over the lamp assembly. Have you taken out the fan over the lamp? If so is it easy to do? I think that the Sony Techs just change all three fans when they get this fault code. I just want to replace the bad component/components or just the one bad fan. If I figure this out I'll send you out the info to get your set going again. Please let me know if you find the solution. Thanks,