Question about 1985 Ford Bronco

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Heater control will not turn defroster just vent

When you try to switch from floor or vent to defroster it will not go to defroster

Posted by Anonymous on

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6 Suggested Answers

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

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  • 1 Answer

SOURCE: No dashboard heat output

The climate control was poorly designed on these cars.

There is only heat on the floor and defrost settings, due to the layout of the ductwork.

Posted on Nov 22, 2008

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chuck943
  • 783 Answers

SOURCE: Vent control

You have a vacuum leak.Defrost is the default postion(no vacuum).
See if you can locate the small black vacuum line that goes inside the vehicle on the passenger side near the heater core. The trace it back,should see it going to a canister then to the intake manifold.Make sure it is not disconnected or broken somewhere.

Posted on Mar 02, 2009

  • 37 Answers

SOURCE: PROBLEM WHEN SELECTING THE DIRECTION FOR THE AIR

Sounds like you have a supply vacuum problem. When you lose supply vacuum to the control head it defaults to defrost.

Posted on Mar 13, 2009

michigan man
  • 3533 Answers

SOURCE: Auto climate controll only blows through defrost & floor,not the

it either has a vacuum line on the back of the unit off or the control unit is bad

Posted on Mar 21, 2009

  • 714 Answers

SOURCE: 2002 Ford Explorer When turned to defrost air

sounds like your door blend actuator which is under the dash and a pain to replace

Posted on Feb 17, 2010

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1 Answer

1997 Ford Taurus front defrost not working


. Air won't blow out of the floor or center vents just defrost ? Do you have manual or automatic climate control ?
Air Flow Control
Air flow control is accomplished in the following manner:
  • Primary control is through the function selector knob mounted on the A/C-heater function selector switch, which is part of the integrated control panel.
  • The function selector knob has the following positions: OFF, MAX A/C, A/C, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST. The A/C-heater function selector switch combines a vacuum selector valve with an internal electrical switch.
  • The vacuum selector valve directs source vacuum to various vacuum control motors (18A318). Refer to the Vacuum Control Diagram , System Airflow Schematics and Vacuum Control Chart .
  • Two internal, single-pole electrical switches are also controlled by the A/C-heater function selector switch. The combination of these electrical switches controls the electrical supply to the A/C clutch and heater blower motor switch (18578).
  • The position of the function selector knob determines the manner in which the system will operate.
  • Each position of the function selector knob is detented for positive engagement.
  • Vacuum Control Motors The vacuum control motors (18A318):
    • are located on the A/C evaporator housing, A/C recirculation air duct and heater air plenum chamber (18471).
    • direct system airflow to the vehicle interior as determined by the remote climate control module or manual override.
    • The five-passenger seating configuration has an additional vacuum control motor mounted on the heater air plenum chamber to control airflow to the rear seat A/C register (19893).


vacuum control motor-i4bq0ig33y1522pr2d2rrkk3-2-0.gif

Jul 09, 2017 | Ford Cars & Trucks

1 Answer

Heater will not blow out defroster only vent or floor. Turn switch but no air out through defrost.


heater control could be faulty or vaccum to control unit is not sufficient or possible air duct abstruction not letting switch from floor to defrost.

Dec 19, 2013 | 2005 Pontiac Grand Am

1 Answer

1996 Montero Heater Blower not working


I assume your heater setting is electric control, if so either your defrost and floor heat switch failed or wire problem. For the air not hot, check the heat control valve on the top of the hose it should be in front of the firewall. I don't know your car is using mechanic valve or electric control valve. Anyway check there first. Good luck.

Nov 24, 2013 | 1996 Mitsubishi Montero

1 Answer

Air conditioning will not switch from defrost vents


Vacuum control motors are used to position these airflow control doors.
SECTION 412-01: Air Distribution and Filtering 2000 Expedition/Navigator Workshop Manual DESCRIPTION AND OPERATION Procedure revision date: 06/17/1999 Air Distribution There are two sources of air available to the air distribution system:
  • outside air
  • recirculated air
Recirculated air is only used during MAX A/C, AUTOMATIC (if equipped with EATC) and OFF modes.
Air distribution within the vehicle is determined by the function selector switch position, if equipped with manual A/C, or is controlled by the electronic automatic temperature control system in the AUTOMATIC mode but can be overridden by the driver if desired. Airflow control doors are used to direct airflow within the heater air plenum chamber. Vacuum control motors are used to position these airflow control doors.
The air distribution system is designed to provide airflow from the defrost nozzle when no vacuum is applied to any of the vacuum control motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak.
Air enters the passenger compartment from the:
  • instrument panel A/C registers.
  • heater outlet floor duct.
  • windshield defroster hose nozzle.
  • side window demisters.
  • rear seat airflow duct (if equipped).
Passenger compartment air is exhausted from the vehicle through open windows or cab air vents.


expedition air flow hvac system-xvcmtr1jbqa4kfrdszeh0lpe-3-0.gif Item Part Number Description 1 18A318 Vacuum control motor - panel/defrost door 2 18A478 Panel/defrost door (full vacuum position) 3 - Defrost airflow 4 - Side window demister airflow 5 18B545 Temperature blend door (full heat position) 6 19860 A/C evaporator core 7 19A813 Air inlet duct door (full vacuum position) 8 - Outside air inlet 9 18A318 Vacuum control motor - air inlet duct door 10 - Recirculated air inlet 11 19805 Blower motor 12 - Vacuum to emission control 13 - Vacuum from the engine intake manifold 14 19A563 A/C vacuum check valve 15 19A566 A/C vacuum reservoir tank and bracket 16 19B888 A/C-heater function selector switch 17 18476 Heater core 18 18A559 Floor/panel door (full vacuum position) 19 - Floor airflow 20 18A318 Vacuum control motor - floor/panel door 21 - Panel vent airflow
Check vacuum control to the panel defrost motor ( vac,diaphragm )

Nov 01, 2017 | 2001 Ford Expedition

1 Answer

04 Buick Regal Heater blows cold And will not cycle on defrost,floor or vent


if it doesnt switch you may have a vaccum leak, but i work for a junk yard and we seel alot of heater controls for this car you may want to get a new or used one from a junk yard

Mar 26, 2012 | 2004 Buick Regal

1 Answer

Problem with air not coming out of vents.


Check for a vacum leak from the engine to the a/c.The color of the hose is black. Also check if the heater control valve hose is unplugged. If you have vacuum the it sounds like the door for the vent/floor/defrost is broken.

Jun 08, 2009 | 2004 Ford Ranger

1 Answer

Air vents and defroster


replace the vacuum mode control switch in the heater control, this is a dealer only part.

Mar 22, 2009 | 1999 Ford Expedition

1 Answer

Switch on dashboard does not change air direction to flow & vents


Defrost is the default mode so if the system fais, you alays have defrost. The mode doors are controlled by vacuum motors. I would suspect a vacuum leak in the engine compartment on the hose going from the engine through the firewall and into the heater controls. Some systems have a vacuum storage canister that can also leak. The canister stores vacuum when vacuum drops going up a hill.
Or, you have a bad heater control head that is not passing vacuum to the vacuum motors on the mode doors.

Here's a diagram of the system for reference.

826b4f9.gif

Feb 15, 2009 | 1999 Ford F150 Regular Cab

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