heat

I get cold air when I turn on the defrost and the car has ran to get the temp up to 125+ degrees. I tried to let it run longer to see if I get warm air and still nothing in the 94 cavalier. What could it be???

The heater core. Expect to unload $1000 for the replacement. You might luck out by reverse flushing the heater core and cooling system, but make sure they disconect the heater core it's self and flush it separately for a long time. Most likely if the passenger side floor is wet under the dash, you will have to replace it all together. Good luck on that. A shop will probably charge you around $100 to flush it, or you can decide to invest that towards the heater core it's self, and in the dead of winter you'll value every cent that went into it.