My friend has a 92 Civic and the A/C blows cold air but when he turns the heat on it doesnt get hot or even warm

 

check coolant level and make sure the heater hose is connected

 

well i just replaced the coolant a couple days ago so it can't be that. Where's the heater hose located boss?

 

thats probably exactly what it is. did you properly bleed the cooling system when you replaced the fluid. try taking the cap off the radiator (when car is cool), turn on your heater and let the car idle until thermostat opens/fans kick on. ensure that your heater hoses are getting hot, and the car is blowing hot air.

your heater hoses are the 2 hoses going from your engine into your firewall, usually around the center of the engine bay.

 

Also, make sure your heater hoses are routed correctly. If the looped hose on the thermostat housing is connected wrong, then you may just be circulating coolant around the motor and not into the heater core. This will cause you to have little or no heat at all.

 

Here is a quick crappy illustration. If the yellow loop hose is not connected like this, and is connected in any other way. Then the coolant will just circulate around then engine.