No heat?
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5th Wheeling
Joined: Jul 2024
Posts: 34
Likes: 1
No heat?
I have a 97 F150 that currently has no heat at all. I’ve replaced the blend door actuator and took a look at the blend door and it’s still in solid shape. My coolants at the right level but still a little brown, I flushed it the best I could a while ago. The heater core is also flushed and the thermostat is brand new also. Any suggestions?
More Turbo
Joined: Sep 2017
Posts: 574
Likes: 146
Check the temperature of the hoses to and from the core. One should feel hot ( the inlet line ) and the other cooler (return line).
If the temperatures seem right then it's not the coolant flow. It's likely the door is not positioning correctly.
If it doesn't seem right, then you have a coolant flow problem and will need to trace the problem back though the system.
If the temperatures seem right then it's not the coolant flow. It's likely the door is not positioning correctly.
If it doesn't seem right, then you have a coolant flow problem and will need to trace the problem back though the system.
Thread Starter
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5th Wheeling
Joined: Jul 2024
Posts: 34
Likes: 1
Check the temperature of the hoses to and from the core. One should feel hot ( the inlet line ) and the other cooler (return line).
If the temperatures seem right then it's not the coolant flow. It's likely the door is not positioning correctly.
If it doesn't seem right, then you have a coolant flow problem and will need to trace the problem back though the system.
If the temperatures seem right then it's not the coolant flow. It's likely the door is not positioning correctly.
If it doesn't seem right, then you have a coolant flow problem and will need to trace the problem back though the system.
More Turbo
Joined: Sep 2017
Posts: 574
Likes: 146
If the heat is not being transferred to the core then the positioning of the door must not be correct. There's no other explanation I can think of. Maybe someone else will have a suggestion.
Fleet Mechanic
Joined: Jun 2023
Posts: 1,365
Likes: 379
From: WA
Here's a couple of vidoes. I'd start by watching the shaft and listening for the door to thud when it opens and closes.
Here's one showing how what a properly functioning door sounds like. At 7:35.
Here's one showing how things work.
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5th Wheeling
Joined: Jul 2024
Posts: 34
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Not clear how you know the blend door is in "solid shape". Did you use a borescope? It's not visible from the outside. Also, have you actually confirmed that the actuator is spinning its shaft? There's a video out there somewhere showing how you can see the shaft of the actuator moving. There's also one out there showing how the bottom of the door at the actuator can be fine but the door itself can be broken off of the main shaft.
Here's a couple of vidoes. I'd start by watching the shaft and listening for the door to thud when it opens and closes.
Here's one showing how what a properly functioning door sounds like. At 7:35.
https://youtu.be/bflILISR1AE?feature=shared
Here's one showing how things work.
https://youtu.be/zmOlDQQXlkw?feature=shared
Here's a couple of vidoes. I'd start by watching the shaft and listening for the door to thud when it opens and closes.
Here's one showing how what a properly functioning door sounds like. At 7:35.
https://youtu.be/bflILISR1AE?feature=shared
Here's one showing how things work.
https://youtu.be/zmOlDQQXlkw?feature=shared
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More Turbo
Joined: Sep 2017
Posts: 574
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My heat blows lukewarm air when the engines warmed up but it goes back to being cold as soon as I turn the fan speed up.
Lead Driver
Joined: Nov 2020
Posts: 7,128
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From: Sportsman's Paradise
I ended up ordering both the blend door and the actuator. I cut behind the glove box to get to the blend door and the actuator was opening and closing the blend door just fine. My heat blows lukewarm air when the engines warmed up but it goes back to being cold as soon as I turn the fan speed up.
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5th Wheeling
Joined: Jul 2024
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Likes: 1
I went back and pulled the cut piece behind my glovebox again and turned my heat on with the engine completely warmed up and there was no airflow through the heater core and it was cold to the touch and the only air coming out was through the AC condenser next to it. Not sure if I should back flush it again to see if that will work or if I should tackle trying to replace the whole heater core instead.
Fleet Mechanic
Joined: Jun 2023
Posts: 1,365
Likes: 379
From: WA
RLXXI was talking about air flow AND/OR coolant flow. Backflushing helps coolant flow but not air flow.
Pretty sure that fresh air from the cowl vents is supplied for every setting except MAX AC. You could have a blockage anywhere from the cowl vents (the grill at the base of the windshield) to the heater core itself. Could be a mouse nest, could be a years-long accumulation of stuff.
Looks you found a target either way. No air flow, no heat transfer. I haven't looked at the F150 cowl vents but typically there's a large cavity under those grills that the system pulls from. I'd start there. Make sure it's clear.
Pretty sure that fresh air from the cowl vents is supplied for every setting except MAX AC. You could have a blockage anywhere from the cowl vents (the grill at the base of the windshield) to the heater core itself. Could be a mouse nest, could be a years-long accumulation of stuff.
Looks you found a target either way. No air flow, no heat transfer. I haven't looked at the F150 cowl vents but typically there's a large cavity under those grills that the system pulls from. I'd start there. Make sure it's clear.
More Turbo
Joined: Sep 2017
Posts: 574
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the heater core and it was cold to the touch and the only air coming out was through the AC
If the heater core is cold to the touch then the hot water is not going through the entire core. Since both hoses are hot there should be some flow through the core. Check the temperature near the top of the core near where the lines are attached. Otherwise something's not adding up....
If it is warm/hot at the top of the core and cold at the bottom then it is clogged. I would try flushing again, (can't hurt ), if it doesn't help at all then it would be time to replace the core.
Fleet Mechanic
Joined: Jun 2023
Posts: 1,365
Likes: 379
From: WA
Another part of the flow path that could be blocked might be the restrictor in the supply hose to the heater core. I don't know much about it but have heard that one exists. If the core flows freely (you haven't really described flow rate through the core - is it a lot, a gusher, or a dribble?) then you might check the supply hose.
If you replace one freely flowing heater core with another freely flowing heater core you probably won't see any change.
Found an old thread about the restrictor. It's basically a plug with a small hole in it. Could easily get jammed with crud. Should be easy to locate, if you have one.
https://www.ford-trucks.com/forums/1...estrictor.html
If you replace one freely flowing heater core with another freely flowing heater core you probably won't see any change.
Found an old thread about the restrictor. It's basically a plug with a small hole in it. Could easily get jammed with crud. Should be easy to locate, if you have one.
https://www.ford-trucks.com/forums/1...estrictor.html