No heat in 1997 Ford F150

This topic contains 2 replies, has 1 voice, and was last updated by Alan Edes Alan Edes 11 months ago.

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  • #895139
    Alan Edes
    Alan Edes

    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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  • #895154
    Alan Edes
    Alan Edes

    Well, it’s been 2 days and 21 hrs since I started this topic and I have yet to get any advice. While that is a bit disappointing, the good news is that I have solved the problem myself simply by not giving up and now I will share what I have done and how I did it.

    I discovered that my thermostat was in fact faulty and so that was the first thing that got replaced. Still without heat, I decided that I needed to flush the heater core. I was only able to remove one water line (the one on the right which is the line IN) from the heater core under the hood at the firewall, the line OUT was not cooperating after trying very hard… so I cut that line, fitted a garden hose attachment to the side still attached to the heater core, attached a scrap piece of hose to the line IN, and attached a garden hose to the line OUT, turned on the water and flushed the heater core.
    The water that came through was pretty nasty and even flushed out some rubbery chunks, probably dried stop-leak or something. After a couple of minutes, the water ran clear and I put everything back the way it was. I repaired the line I cut with a brass hose part and two hose clamps from the hardware store.
    Next, I needed to temporarily repair the blend door. There are a number of videos on YouTube that show how to do this, but since I haven’t gotten the new blend door yet, I decided that I needed to get the old one into the open position and make it stay there until I can replace the door. I cut the holes as per the video instructions, got the blend door in place, and found a way to keep it in place with a huge socket that happened to fit in there and is heavy enough that it isn’t likely to move. If someone else wants to try this, you’ll just have to get creative and find a way to secure the blend door open. BUT DON’T GLUE IT!
    Next, I just had to close the hole that I cut in the heater core box using the piece of plastic that came from there. A little duct tape and success!
    My heater works VERY WELL, it was a total success! For now, I cannot adjust the temperature, but as soon as I get the new blend door, I’ll fix it properly and have full use of the heater and temperature control.
    Now I will attempt to upload a few photos I took.
    The photos are as follows:
    1: holes cut behind glove box and in heater core box.
    2: camera view inside core box looking at bottom of blend door in open position.
    3: camera view inside core box looking at top of blend door in open position.
    4: camera view inside core box with huge socket in foreground holding blend door in open position.
    5: hole in heater core box closed up and duct taped.
    I hope this information helps someone some day and I would welcome any questions if additional information is requested.
    Alan aka Whitewolf

    Alan Edes
    Alan Edes

    The photos did not load in the order that I intended. Their order is:
    1, 2, 5, 4, 3

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