I have a 91 LeSabre that i cannot figure out why the heater doesn't blow hot air, it's only SLIGHTLY warm. I changed out the heater core and thermostat to no avail. This car does not have climate control, just the slide lever to choose heat, def., a/c, ect. Anyone have suggestions where to look?

Thanks. Just found this site. Wow. Alot of info here. Thanks again.

 

The first question I would ask is, after the engine has been running a while , do the heater hoses get hot?
If yes, then there is a blend door that may be stuck in the cold position not directing all incoming air over the heater core.
If the hoses are not getting hot, suspect the water pump for a worn impeller or all the air is not out of the heater core.
You should have a 195 degree thermostat in there, do you?
And last, just to cover all the bases,the cooling system is full correct?