Guys, I have a 91 accord that once in a while, the interior fans will not switch on. I notice this on the hot days when I need my A/C. 8/10 times, once I turn the fan knob, the fans start blowing but there are also days when nothing happens. Today, it failed again...I just left the fan switch on position 3 and after 10 minutes of driving, they started blowing again. Any idea what's causing this?

TIA