Hey guys this is non-3rd gen!

I have a 84' Caprice Coupe and my heat was working perfectly until today. Now nothing but cold air is coming out of my vents. The only mods I have is a new carb, alternator, and battery.DOES ANYONE OUT THERE HAVE A DIAGNOSIS FOR THIS PROBLEM?

 

if your blower motors still working its probably a blockage in the cooling system, most likely buildup in the heater core.. other possiblities would be a low coolant level, but you'd probably notice a leak or something if this just came on.. i'd say blockage in the heater core.. try flushing the cooling system

 

Possibly a heater control valve.

Somewhere in between the radiator and the heater core (firewall) there may be a black valve in the heater hose. If there is, then more than likely that's the culprit.

If there isn't one there, check the level of your antifreeze. If it's low, there isn't enough in there to heat up anything, including the engine.

 

Yup, check the vacuum connection to the heater control valve. Right next to the carb.

 

Also, it could be a bad flapper door/related control hardware that splits the air intake between cold outside air and air that gets drawn through the heater core. On the Caprice I think it' just a cable that's hooked up between the hot/cold control lever and the lever that works the flapper under the dash. I've seen the arm on the flapper door itself also break.

Um....... ya know, if you have a coolant leak and drain most of the coolant out of the system you can also end up with a no-heat situation shortly before you overheat the motor, too. Just thought I'd throw in the super-obvious.

 

Or maybe its as simple as a thermostat.

 

Got coolant?