No hot air from heater

Tiny
BLACKOP555
  • MECHANIC
  • FORD F-150
Ford F-150 1987 5.0L V8 93,000miles: I have just recently replaced my heater core in my truck. The problems is that there is no hot air coming from the heater only mild heat. It is barely enough to take fog off the windows. I felt both hoses to the heater core (in and out) they are both hot to the touch. With that I suspect that is not the valve's that regulate heat to the heater core. I am at a loss I would like to see what you have to say thanks
Tuesday, April 3rd, 2007 AT 8:07 PM

13 Replies

Tiny
PEPPERMRJ
  • MECHANIC
  • 1,158 POSTS
If I remember correctly the heater controls use vacumm motors to direct airflow and open and close the door between ac and heat. Check that all ines are attached and you have vacuum. I had a vacuum line on my windstar at work break inside the tube thru the firewall. PITA.

Good luck and let us know. :)
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Tuesday, April 3rd, 2007 AT 8:50 PM
Tiny
BLACKOP555
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There is no ac
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Tuesday, April 3rd, 2007 AT 8:57 PM
Tiny
PEPPERMRJ
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No matter. The door that directs airflow from the floor, to the vents, to the defrost position could be stuck inbetween limiting airflow. Can you hear the door change position?
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Tuesday, April 3rd, 2007 AT 8:59 PM
Tiny
BLACKOP555
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Yes sir. I can hear the door and I can also feel the air flow change. The air is comign out good it just ALMOST warm not quite warm its bout the middle setting on a average vehicle
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Tuesday, April 3rd, 2007 AT 9:04 PM
Tiny
PEPPERMRJ
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Ah I get it. Low fluid level, a stuck open thermostat, air in the system, poor belt tension to the waterpump pulley or a bad waterpump can cause this. Did you flush the system?
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Tuesday, April 3rd, 2007 AT 9:15 PM
Tiny
BLACKOP555
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I have checked that. Waht I dont understand is why the in hoses to the heater core is hot and the one out is hot. Wouldnt that indicate the stuff u listed above is in check?

Yes the system has been flushed also.
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Tuesday, April 3rd, 2007 AT 9:18 PM
Tiny
PEPPERMRJ
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You would think. Maybe not good water flow tho. Blockage somewhere. Try reverse flushing the heater core.
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Tuesday, April 3rd, 2007 AT 9:20 PM
Tiny
BLACKOP555
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My dad told me he tryed that. Still the same temperature

i beleive the thermostat is good because the temperature is almost all the way to the top of noraml operating

also I have removed one of the hoses and turned on the engine there was a good flow comign out and I tryed on the other. Same thing
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Tuesday, April 3rd, 2007 AT 9:22 PM
Tiny
BLACKOP555
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So IMHO I think that it is duct related. Is there a way to bypass the system just to put out hot, and if it is then I know its related to the controls? Or if it is cold then there is something related to something outside the cab in the cooling system?
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Tuesday, April 3rd, 2007 AT 9:28 PM
Tiny
PEPPERMRJ
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Well if you have good flow, correct fluid level, correct operating temp, no blockage or air bubbles, and properly operating air controls, you have good heat. Go back to the beginning and start again. Missing something. Heater hoses are attached correctly? Have the temp checked with a laser gun. 185 or better.

Good hunting and let us know. :)
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Tuesday, April 3rd, 2007 AT 9:29 PM
Tiny
BLACKOP555
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I just think I foudn it there is a tab that is snapped off on the plastic door that turns when adjusting the amount of heat or cold. The heater core is really hot to the touch I think ill have to replace it.

Thank you for ur help m8
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Tuesday, April 3rd, 2007 AT 9:38 PM
Tiny
PEPPERMRJ
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Wow thanxs for the speedy update.
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Tuesday, April 3rd, 2007 AT 9:39 PM
Tiny
BLACKOP555
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Lap top in the garage for the win. I hate it when people dont update me so I figure I can atleast do the same for you.
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Tuesday, April 3rd, 2007 AT 9:40 PM

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