Heater motor works but no heat is coming into cab.

[RDF]

I am having a problem with my 1991 Chevy S-10. The heater motor works (I took it out and tested it), but no heat is being generated for defrosting and warming the cab. It's like its being blocked or something.
There is some vacuum power, but it is not heavy. I don't use the AC.
I need some suggestions ASAP.

Thanks,
RDF

[OverBoardProject]

when it's in the car can you hear the motor spinning? if you can then there is some blockage, and it could be anything fron a mouse nest in there to none of the doors opening. Look at the doors first since it's usually easier to find (there is always some external linkage under the dash)

If you can't hear the motor spinning then you'll have to look at the wiring.

I hope that you have a heated garage to work in

[dwools]

Sounds like the heater core. Mine just went bad also. I get no heat, no defrost, but the temp stays good. This means that the thermostat is working. A new heater core is about $35-$40 dollars at Auto Zone, but is about a 3-4 hour job to replace. A garage will say 5-6 hours of labor, so you have to decide if you are up to the challenge. Good luck !!