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Heater Vent Control

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#1 Curt


    Where's My Hammer!?!

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Posted 09 March 2010 - 07:04 PM

I replaced the heater core in my 1989 F-Series, and now the venting system will not change from vent, to floor, etc. It is stuck on windshield vent. I noticed that a very thin line (I think it looks like a vacuum line) under the hood is broken. It goes to something next to the fan blower, but I couldn't find anything in my Chilton's manual to explain what it is. Any thoughts?

#2 lostin90s


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Posted 11 March 2010 - 04:15 PM

thats one of the controls if it is a arm linkage on top . Patch with rubber line. Also check under dash for loose stuff. Good luck
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#3 Mistyjack04


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Posted 03 November 2017 - 03:11 PM

1996 F250 Heater will not change from cold to heat, heater hoses are HOT, blows cold air!! Thanks

#4 miesk5


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Posted 04 November 2017 - 06:57 AM

Yo Mistyjack04,


Blend Door Cable or Door is also referred to as Temperature Control Cable or Door.

Lack of Heat, The Cable Controlled Temperature Blend Door's Cam Spring Does Not Allow Blend Door to Seat Properly. 

NOTE: The temperature door can be set to full cool, full warm or anywhere in between. The function control knob does not affect the temperature blend door; this is governed by the temperature control knob.


Blend Door Location in a 94; 80-96 similar; "...Probably the temp blend door is loose & flopping around on its own. The easiest way to see it is to fully lower the glove box, pull the ~8 screws from the heater core cover, & look inside to the L (driver's side). You'll see the cable & control lever (in top L of 2nd pic) as soon as you fold the glovebox down, so inspect it first. The 3rd shows the whole cover - it's the large section in the top center with tiny white numbers inked near its bottom edge. The cables are visible, too...."

See these for more diagrams;



The temperature control knob may be difficult to turn on some vehicles.

There may also be a low or no heat/cooling condition accompanied by poor temperature modulation. This may be caused by the single cable temperature door operating system being used.  But your 96 Should have the new dual cable.


Blend Door Control Cable Location pic for 92-96 Bronco & F Series


On 87-96 trucks, it's easy to fold the glove box down & pop it off its hinges or move it back into position.



Blend Door Control Cable pic in a 92 
Source: by 2bet




In the FLOOR position, the OUTSIDE AIR door is open. Airflow is directed through the TEMPERATURE BLEND door opening, through the heater core (18476), past the closed FLOOR/PANEL door and out through the open FLOOR/DEFROST door to the heater outlet floor duct (18C433). There is also an air bleed past the closed FLOOR/DEFROST door to the windshield defroster openings. Read more @ http://www.diesel-da...tj/stjc2007.htm


Here is the 96 F Series/ Bronco Workshop Manual, partial by diesldave @ http://www.diesel-da...stj/stjleft.htm



But this section doesn't address the Blend Door Cable or Door,  also referred to as Temperature Control Cable or Doorbecause Ford didn't want to get past routine issues.

Section 12-00: Climate Control System, Service
Symptom Chart — Climate Control System
  • Insufficient, Erratic, or No Heat
  • Low radiator coolant due to coolant leaks.
  • CHECK radiator cap pressure. REPLACE if below minimum pressure. FILL to specified coolant level. PRESSURE TEST for engine cooling system and heating system leaks. SERVICE as required.
  • Engine overheating.
  • REMOVE bugs, leaves, etc. from radiator and support or A/C condenser core fins. CHECK for:
    • Operation of engine fan clutch
    • Loose drive belt
    • Sticking thermostat
    • Incorrect ignition timing
    • Water pump impeller damage
    • Restricted cooling system
    • SERVICE as required.
  • Loose drive belt.
  • REPLACE drive belt if cracked or worn and ADJUST drive belt tension.
  • Thermostat.
  • FEEL heater water hoses. If the heater water hoses are too hot to hold, the thermostat is OK. If the heater water hoses do not get too hot to hold, REPLACE the thermostat. If only one heater water hose gets hot while the other remains cool, a plugged heater water hose or heater core is indicated.
  • Heater water hoses.


Suggest you join us at http://broncozone.com. It's  our sister site. The owner may merge this Fordfzone into there or delete due to low membership use here.

Be well!


96 Bronco, E4OD, Man Xfer Case & Hubs
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