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Heater constantly on!

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Old Aug 8, 2018 | 04:16 PM
  #1  
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James Wade
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Heater constantly on!

Hi all,

New to this forum, and starting out with an odd issue. I've searched around a bit, and haven't found a thread quite like what I'm experiencing, though being new I could have missed it.

2004 f350 6.0

My heater seems to be constantly blowing to some extent, and usually from the feet when set in the off position. It is also constantly blowing hot air and the ac wont work either. I can switch the positions of the fan from feet, to dash, to defrost etc, but not the temp. The ac may be leaking in combination with whatever is going on, as I had it recharged a while back and it didn't seem to last. (This was prior to the heater being on constantly). Hoping there is something simple, as it's around 95 degrees out and I work from my truck!

thanks
Joe
 
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Old Aug 9, 2018 | 09:19 AM
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The blower motor should run in all MODE switch positions except OFF when the ignition switch is in the RUN position. Verify this works correctly.

Put the MODE switch in the VENT position, then exercise the TEMP control through its full range with the blower running. You should be able to vary the temperature from < bleeping > hot (fully CW) to a bit above ambient (fully CCW), assuming a warmed up engine and fully operable controls. Verify this works correctly. If it doesn't, check first for a stripped TEMP ****, then check behavior of the temperature blend door.

Check to see if the truck is equipped with a heater hose cutoff valve. If so, it should operate when the MODE switch is in the MAX AC position and cut off all coolant flow to the heater core.

If the refrigerant has leaked out of the system, obviously the A/C will not function. Have the system checked by a competent technician if you're not familiar with how to do it. If discharged again, have the leak repaired.

 
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Old Aug 9, 2018 | 10:35 AM
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James Wade
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When my heater is set to off, air still seems to emit from the feet position. It doesnt feel like the fan is blowing, but more accurately "leaking". It is always hot, even when the dial is set to cold. I have taken my glove box out and listened while adjusting temp and it doesnt appear anything is moving.
 
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