Just bought it off here at MP, my question is how do I know if the esc fan is bad? it doesn't come on when I switch on, it's the older model mmm1, thanks...

I've had a couple of MM1's, and i remember the fan to come on just briefly when the esc was turned on, and then stop.

I think at power on it does a brief spin-up but only comes on when the ESC is warmed up from running.

The fan can be replaced, or you can replace the case and fan for that new look. Neither are an expensive path if you suspect the fan is bad or going bad.

A couple of racers at our track does not care if the fan is working or not, because geared correctly, the esc doesn't need the fan.