Heater will not blow out hot air in my 1988 ford F250. Thermostat and hoses are all good. Is there a sensor that may be causing the problem and where is it located?

Hello! There isn't a sensor that would disallow heated water to circulate through the heater core...If the temperature gauge rises to normal...And the upper radiator hose is hot along with the lower hose ...I can conclude water is circulating through the block...Question then becomes; Is it circulating through the heater core? And the answer to that is, I don't think so...With the heater control turned on high feel the outlet heater core hose (facing engine it's the one on the left) if it feels cold or not as hot as the inlet then one of two items are at fault...#1...The Plenum assembly, which the heater core sets in has an open vacuum line...#2...The heat control valve cable or the valve itself is not opening...See picture of valve below...It is on the firewall...Let me know if heat is passing through the heater core...If hot water isn't passing through the core and the valve is opening than the core itself is blocked...send a comment...Guru...Saailer

MOTORCRAFT Part # YG229...$20

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