i have a 1999 integra there is no hot air coming. The fan works, fuse ok, relay under hood ok, hot/cold lever works, a/c works, all I'm getting is cold air. Any idea as to what could be wrong.

 

your thermostat is stuck open, replace that. but if that doesn't fix it your heater core might be clogged. just try the thermostat first because it's only a couple bucks compared to taking out your dash to replace you heater core

 

the thermostat on the engine which controls the water coming from the radiator is fine. Is there another thermostat on the heater blower assy? or you think the relay on the blower assy. is bad?

 

let the car idle and feel your bottom radiator hose, if it doesnt get warm that will prove its the thermostat.