I have a 1994 GMC K1500 Extended Cab Pickup with a 5.7L V8. I am having a problem with the heater working at its full capacity. The coolant level is good, I replaced thermostat recently with an OEM temperature thermostat, the heater core was replaced within the last 10,000 miles, and the blower motor works at all speeds. I am running the heater on high and the passenger compartment is not getting warm. I have had the dash and heater box out recently, replacing the evaporator, and I feel that I put everything back together correctly. My blower motor works at all speeds, the blend door actuators are working because I can hear them switch and feel air at the desired locations, but it is not warm. I currently have no refrigerate in the system because I need to replace the A/C compressor. I have always heard that the coolant level, thermostat, and heater core are the common causes for heater problems. Does anyone have any suggestions?
