Hello

I have a 04 mazda mpv with no heat, all i get is cold air blowing out. I have flushed the heater core and I have coolant flowing through it. What else can it be? Please help it's getting cold out

 

Thermostat.

 

I recently had this problem in my 99 Mazda.
Problem was the door/baffle on the heat exchanger box was stuck closed.
On most cars the coolant continuously flows through the heat exchanger under the dash but when no heat is called for, the box is shut off to air flow.
I found my actuator motor in the middle of the lower dash. It was accessable by removing my sound system assembly. A little push on the one of the levers while calling for heat got it working. From now on I will try not to leave it closed off for so long (all summer) so that it hopefully will not get stuck.
To get into the dash I just keep popping panels off and undoing screws.