I have a 1993 Chevy c/k 1500 I just replace the thermostat replace the heater core both sides of the holes are getting hot and no heat blows out the vents just luke warm air on defrost vent and floor
Is your fan working correctly, I mean is it running ip to speed? Are the vents connected.
Blend door actuator?
If you have a heater control valve it may be only opening part way or clogged. Some vehicles use a heater control valve to shut off the coolant flow through the heater core when a/c is selected. Some valves are vacuum operated while others are cable operated. It could also be the temperature door under the dash is not going to the full heat position. In '93 I believe it would be cable operated. One end of the cable hooks to the temperature lever on the dash and the other end to the temperature door under the dash. Since you replaced the heater core the cable may need to be adjusted to give full heat. HTH. -Jim
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