The relay is powered up and activated thanks to a small electrical current. When it is activated, it lets a current that is much bigger than the original one flow through other two outlets. It is used to control the headlights, the rear fog light, the electric fan, etc.
AC compressor won’t come on, no relay in that car for AC or I just can‘t find it, the AC was working great and all sudden while I was speeding to get on highway from in ramp the AC went warm!