That's an optical transistor that runs that wheel. It uses and led to work, it's that big black transisor.
One, you can see if you have 5V to the optical board. If you do, then you need to clean the slot. Take it out and clean the inside of the optical slot.
If that doesn't work, your board is dead and you need to find a new one. I don't think you can get it fixed unless you can find an ECG part to replace that transistor.
They cost about $10 bucks, and you can find one by asking on RGVAC.