Hi, I have a 1997 Ford F150 w a 5.4 litre engine. The air is ice cold when the heater is turned on.
I have grabbed the water lines under the hood and both feel hot.
I have checked the blend door switch and verified that it is working properly and in the process discovered that the blend door is broken.
I watched several videos on how to replace the broken blend door and am satisfied that I could do that successfully although I haven’t done that yet.
A previous owner of my truck has cut a small hole below the dash that allows me to see the blend door and the mechanism that opens and closes it and the hole was stuffed with paper towels, I assume to hold the door closed. However after removing the paper towels and looking through the hole to verify the broken door, etc, I was able to push the door open and can see the heater core beyond.
So… I should have heat circulating now with the door open (and a lot of air blows out that hole of course), but the air is ice cold.
Question: Is it likely that the heater core is plugged and no hot water is getting in there?
I will fix the blend door asap, but it is definitely open.
Question: Could the cold air also be caused by a faulty or missing thermostat? (Since the heater core water lines felt hot, that doesn’t make sense, but maybe could contribute to the problem?)
Thanks in advance for any advice or tips. Alan
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