A real close up of a fresh air heater core and control valve! Most have not seen this combination in their original GM truck unless repairs were needed.
Thus, this may be of interest to some owners. This is how GM heater designers were able to incorporate an in-dash control cable to the water control valve. They created a water control valve that attached to a right angle bracket on the top of the core. This core and the delicate valve are protected by the sheet metal heater box. Unless repairs
are needed, none of these internals will ever be seen.
Once heated water from the engine enters the valve (to be flow adjusted by the dash control cable) it goes to the thick square heater core.
The heater fan forces air through the core fins. Here air is immediately warmed, depending on the speed of the water flow. The slower this flow, the more hot liquid can heat passing air from the fan.