I just recently bought 2002 Mazda 626 and there is water leak appears all the time on the passenger side.Any ideas why?
It doesn't matter if I dry it out every day, still leak appears 1-2 days after.

 

If it's water (not coolant, which is sticky) it's condensation coming off of the AC system. It's completely normal.

 

I forgot to say that it appears on the carpet (passenger side)

 

Could be the heater core. It should be coolant not water if that's the case though.

 

Theres an A/C evaporator drain on the right side. Check to see if its unpluged and if its plugged in make sure it is draining to the outside. Leaves can get in the evap and clog the drain. Compressed air blown into the drain hose will usually unclog it.