This sounds like a power supply issue. Are you able to test your power supply (DVM)?
Some things I strongly recommend is making sure the AC outlet is properly wired & grounded as well as using a surge suppressor or better yet a good UPS. Often times surges can weaken or kill a systems power supply. It makes no difference what the system is, computers are just sensitive!
You’ll want to gain access to the power bus bars as you can see in Step 20 in this guide [guide|21212]. Follow the first steps stopping at Step 8 so you can then remove the shield. Then reconnect the fan unit making sure you don’t stress the connections (very easy to damage) using the DVM measure the voltage across the two sets of screws make sure you son’t short the contacts! What is the voltage you’re measuring?
To be clear here this is not easy to do by your self! Using a second set of hands makes this much easier.