Ok, so my fan isn't working for some reason, how can I go about figuring out if it is the relay or the actual fan motor?

I can drive for a while before the actual temperature goes up, about 5-7miles, because the fan seems to start on initial startup, but not every time. I've just noticed that I can go for a little bit and have the temp stay normal, then it seems to jump around 190 for a bit, goes up and down very slightly opposed to staying on 190. So how can I figure out if it is the relay or the motor in for the fan?