I have a Saike 898D, basically a re-badge of the same model. My hot air gun died one day, fan would work intermittently, but in my case the heater and fan was ok. The cheap cable on the device was a fault. Broken cable. I replaced the cable with some 12 core I had on a reel, and got some new connectors to crimp on for plugging in inside the device.
So, First, I would buzz out the cable, before condemning the electronics.