Yesterday, in my 85 S-10 pickup, the heat seemed to be LESS. Today, it was almost nil. Not that there has been a lot of heat in the car, but since I changed the thermostat this fall, there has been some warm air available from the heating system (in contrast to last winter when there was almost 0 heat from the thing).

The fan is working and the blower blows. The air seems warmer than outside air, but that's not saying a lot since outside it has been around 10-20F.

I don't know a lot about the heating system, so don't have any idea about what to consider doing to the car to fix it or at least improve it. Any suggestions would be appreciated. Thanks.

 

check both heater hoses to see if they're hot. If yes then it could be diverter or blend gates not working and inturn not pulling the air through the heater core.
If the hoses are cold(warm not hot) try another t-stat or cover a part of the radiator(not all) with cardboard just remember its in there next spring

 

And if one hose is hot and the other is cool, chances are that the heater core is plugged.

 

I appreciate the suggestions. Many thanks. I'll check the car out and see what I find.