Question about 2003 Chevrolet Astro

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Climate control the selector for defrost, heater, vent, A.C, does not work. the knob turns fine, you can feel the detents inn the swithch, but the system does not respond. The vehicle is a 2003 chevrolet astro.

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There is a vacuum line that operates your selector switch, it is located under the hood, roughly in the center, up against the fire wall. If the line has leaks, your selector switch will not work and therefore all your blower doors will stay shut. Replace the line.

Posted on Jan 01, 2009

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Check your fuses and relays

Posted on Dec 06, 2008

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1 Answer

Mode selector control switch will not change from vent to defrost or floor heat. 1999 Ford Crown Victoria.


If it's cable driven, the cable may have broke the plastic piece it's connected to behind the knob not allowing the turn knob to turn the blend doors through the cable. To find out you will need to take the center trim off and remove the climate control box" the one with all the knobs on it", and see if the cable is connected. Be careful pulling it out as the box will have to be twisted to get to where the cable is attached, very easy to break the plastic pieces as the have been introduced to heat over the last 17 years which degrades the plastic. Hope this helps. Also utube how to remove the climate control unit as this can be very helpful

Oct 07, 2016 | 1999 Ford Crown Victoria

1 Answer

Why does turning vent knob (defrost, mix, dash,floor,etc.) have no effect?


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1 Answer

Why wont my 2001 ford windstar blow out of vents ? only on defrost?


Air Flow Control
Air flow control is accomplished in the following manner:
  • Primary control is through the function selector knob , mounted on the heater function selector switch, which is part of the heater control .
  • The function selector knob has the following positions: OFF, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST.
  • The 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 System Airflow Schematic and Vacuum Control Charts.
  • An internal single-pole electrical switch is also controlled by the selector. The switch controls the electrical supply to the 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.
  • You probably have a vacuum leak , Pull heater control panel an check for vacuum . A broke vacuum hose or The vacuum selector valve is bad ! Or check for a vacuum hose in the engine compartment being off somewhere !

Mar 08, 2015 | 2001 Ford Windstar

1 Answer

Defrost not working


Hello, and welcome to fixya! The reason that you are able to hear the climate control system and not feel the air coming out of the defroster, is that the damper (this controls where the air is directed when you change the vent selection on the climate controls) is not operating as it should. The damper is controlled by vacuum pressure, and the usual culprit is that the vacuum hose running to the damper is either loose, or defective(usually dry rotted) which will create a vacuum loss. Without the vacuum pressure to operate the damper, you will lose some, but not all functionality of the vent selection. I recommend that you check the vacuum line(s) that run to the damper, making sure that the vacuum hose is connected, and free of defects, like cracks, holes, and that the connections are not loose as hoses can and will lose their elasticity, which will create a vacuum loss. If that is not the issue, I recommend that you remove the climate control vent selector and make sure that all of the connections to the control panel are secure and free of defect. If that is not the issue, you may have a faulty damper (which is rarely the case), and that will need to be replaced. As far as the climate control lights not working, that could be a simple as a blown fuse, faulty bulbs, or even as simple as a poor connection to the bulbs, or to the control selector. I highly recommend that you disconnect and reconnect all of the connections to the unit. When you check the fuse panel, remove the fuse(s) & check for faults and make sure that the connection the fuse is making in the fuse panel is making a solid connection. I hope that you have found this information useful, are able to resolve the issues you are experiencing.

Jan 27, 2014 | Dodge Avenger Cars & Trucks

1 Answer

My ac and heater are stuck in defrost and i cant figure out why i turn the dial to vents and heat but it stays in defrost


It all depends on whether your truck is equipped with Automatic Climate Control or Manual HVAC. You could have a broken control head assembly a broken mode door cable, a failed electronic mode door actuator, a broken mode door, or a loose or broken wire or connector.

To put it simply, your mode doors are not swithching modes - the reason for this can vary depending on which system you have.

Nov 14, 2011 | 1999 Chevrolet Silverado 1500

1 Answer

My blower only blows threw the defrost vents. all climates everything, no matter where i put the control knob. dealership says the solenoid got stuck closed after using my 4 wheel drive.


Assuming you have vacuum controls at the heater control head, you have a classic vacuum leak in the hose from the engine intake manifuold to the control head, or the vaccum storage canister somewhere in the engine compartment. It is required to fail to defrost by law.

Climate Control Assembly
The climate control assembly has 3 system controls:
  • The function selector switch combines a vacuum selector valve with 2 electrical switches to supply battery positive voltage (B+) to the blower motor control circuit and the A/C clutch circuit (if equipped).
Vacuum Control Motors
The 2 vacuum control motors:
  • are actuated by vacuum from the function selector switch.
  • position the plenum doors to direct system airflow to the vehicle's interior as determined by the function selector switch setting.
The vacuum reservoir is behind the driver fender well, black plastic ball.

If you have diesel, then you will have a vacuum motor under the hood.

please rate if this helps.

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Oct 05, 2011 | 2006 Ford F-250 Super Duty

1 Answer

Floor heat does not work but defrost etc works is that still a heater core replacement?


If you have warm air coming through the defroster vents then your core is not gone. there is something blocking or bent on the heater box mechanism which directs the air flow up or down, or on the climate control knob which controls it, or in the cable which connect the two.

Nov 26, 2010 | 2000 Chevrolet Blazer

1 Answer

2000 gmc sierra 1500 5.3 v8. a/c heater control problem


your heat/cool and vent selection options are controlled by engine vacuum through small clear tubes attached to the rear of your climate control interface. Other vehicles have small steel pull wires that operate the desired changes. You might try removing the trim and any fasteners affiliated with the interface/console. GENTLY pull outward and look to see if any of these tubes are pulled off or cut/damaged. Did anyone recently install a new stereo in the vehicle? If so, the vacuum tubing and or pull wires that change your outlets could have been damaged when the stereo unit was pushed into place. Hope this helps

Sep 09, 2009 | 2000 GMC Sierra

1 Answer

I have the same problem with my windstar blower is fine but is coming cold air but no heat i dont know what to do can any one show me how to fix it thnx


First, feel the heater hoses going into the firewall under the hood. If they are hot, then you have hot engine coolant going into the heater core. If they are not hot, then you either have a bad thermostat or you are very low on engine coolant.

Next you need air flowing through the heater core so it can come out heated through your vents. If the iar is flowing somewhere else, your temp blend door is not moving because the bend door motor is bad or your temp knob on your heater controls is bad. The blend door motor is an electric motor.

------------------------------------------------
Air Flow Control
Air flow control is accomplished in the following manner:
  • Primary control is through the function selector knob , mounted on the heater function selector switch, which is part of the heater control .
  • The function selector knob has the following positions: OFF, PANEL, PANEL/FLOOR, FLOOR, FLOOR/DEFROST and DEFROST.
  • The 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 System Airflow Schematic and Vacuum Control Charts.
  • An internal single-pole electrical switch is also controlled by the selector. The switch controls the electrical supply to the 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.
Temperature Control
The temperature control operates in the following manner:
  • Temperature control of the heater system is determined by the position of the temperature control knob (between COOL-BLUE and WARM-RED) of the heater control .
  • This control knob is connected to a potentiometer mounted in the heater control . This potentiometer is electrically connected to the electric blend door actuator that operates the A/C air temperature control door.


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  • Movement of the control knob from COOL (Blue) to WARM (Red) causes a corresponding movement on the air temperature control door and determines the temperature that the system will maintain.
System uses a reheat method to provide conditioned air to the passenger compartment.
  • All airflow from the blower motor (18527) passes through the A/C evaporator housing .
  • Temperature is then regulated by reheating a portion of the air and blending it with the remaining cool air to the desired temperature.
  • Temperature blending is varied by the air temperature control door, which regulates the amount of air that flows through and/or around the heater core (18476) , where it is then mixed and distributed.
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inside you plenum box:

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Mar 03, 2009 | 1998 Ford Windstar

1 Answer

Heater works ok but wont send air thru defrost vents


check the control knob it may appear to be working but is not turning the actual controller

Jan 01, 2009 | 1995 Pontiac Grand Am

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