Heater is blowing cold air.

One day my heater is working fine then the next I'm getting cold air. Temp gage reads in the normal, blower, and AC is working but no heat. New to the do it yourself repair arena but where is the the thermostat or is there some other problem lurking?

sh*t sucks for you, I had the same problem with my 89 grand. It is 1 of 3 things. It is either your water pump, check for leaks, if there are leaks it is either your heater coil or water pump. If not than it's your thermostat. If it is your heater coil and you have an 89 or that body style your coil is on the passenger side behind the dash in a plastic box, It's huge you can't miss it.

Repairs:

1) dissasemble your dash, I literally mean totally dissasemble your dash.

2) go into engine bay on the firewall there are some bolts

3) plop open the box and pull it out. My steel hose connecting to the line was stuck and that sucked.

4) This project sucks but it will absolutely suck to repair. Took me many, many hours. Remember where the screws went.