Question about 2002 GMC Sierra 1500

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Heater control will be set on defrost but air comes out panel or switches. floor air is very little.

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  • 18 Answers

Sounds like you probably have a bad vacuum line on the back of the heater control. If you remove the heater control from the dash, you will find a vacuum hose cluster attached, you may either have a vacuum line that has come loose or one that has a hole in it. If you don't find either of these problems, then you may have a bad heater control, but I would look for a bad vacuum line first.

Posted on Nov 17, 2013

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Posted on Jan 02, 2017

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bunnydawg
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SOURCE: 2006 Envoy SLT air suddenly stopped blowing from vents

the resister block needs changing... oddly enough i'm unsure of what fan you are saying is not working.... if it's the front.. the resister block is located on the duct work under the dash for the air... near the fan... you will see a connector going into the side of the duct work. two screws and the block comes out... should be fairly obvious for the rear one but it will be near the fan.

Posted on Apr 16, 2009

alicantecoli
  • 22219 Answers

SOURCE: a/c and heater only blow air out of defrost

either a vacumn pipe is broken or the ends split so its not passing a vacumn to open the flaps,where they are and how to get to them i cant help because i have never worked on one as they are not here in spain.check the engine end first though .Look for some small rubber pipes running from the inlet manifold

Posted on May 30, 2009

  • 6 Answers

SOURCE: 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

Posted on Sep 09, 2009

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Need pitcure of vaccum lines on 1999 Ford Ranger v6 3.o air and heat blows only threw the defroster.


26392097-cvaukpwazi2vnl4fgradjhua-2-2.gif

Item Part Number Description 1 18A318 Vacuum Control Motor-, Panel/Defrost Door 2 18A478 Panel/Defrost Door (Full Vacuum Position) 3 - Defrost Air Flow 4 - Side Window Demister Air Flow 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 18527 Blower Motor 12 19A566 A/C Vacuum Reservoir Tank and Bracket 13 - Vacuum from the Engine Intake Manifold 14 19B888 A/C-Heater Function Selector Switch 15 - Vacuum to the 4x4 Hub Solenoids 16 18495 Water Diverter Valve (Full Vacuum Position) 17 18476 Heater Core 18 18A559 Floor/Panel Door (Full Vacuum Position) 19 - Floor Air Flow 20 18A318 Vacuum Control Motor-, Floor/Panel Door 21 - Panel Vent Air Flow

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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

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

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

Climate Control - Heat and cool work fine. Air flow is directed to defrost /floor. No indication (Sound or sight) that the vacuum diaphrams are being activated. The display on the dash matches the...


Does your vehicle have manual or automatic climate control ? You system is stuck in floor an defrost mode ?

03 mercury grand marquis hvac air flow .-13qahwfdndst2y1hypmr2cdq-4-0.gif Item Part Number Description 1 18A318 Vacuum control motor-floor/defrost door 2 - Defrost air flow 3 18A478 Floor/defrost door 4 18476 Heater core 5 19860 Evaporator core 6 19805 Blower motor 7 - Outside air inlet 8 19A813 Air inlet door 9 18A318 Vacuum control motor-air inlet door 10 - Recirculated air inlet 11 18B545 Temperature blend door 12 18A559 Panel door 13 - Panel air flow 14 18A318 Vacuum control motor-panel door 15 - Floor air flow 16 - Vacuum from the engine intake manifold 17 19A563 A/C vacuum check valve 18 19A566 Vacuum reservoir tank and bracket 19 19980 EATC control
Pull the control panel an check for vacuum

vacuum lines hvac 03 grand marquis-13qahwfdndst2y1hypmr2cdq-4-2.gif Item Part Number Description 1 White Air inlet door 2 Yellow Floor/defrost door 3 Red Floor door 4 Blue Panel door 5 Black Source vacuum 6 - Not used


VACUUM APPLICATIONS CHART-ELECTRONIC AUTOMATIC TEMPERATURE CONTROL Switch Port Vacuum Harness Hose Color Func- tion Manual Override Selector Buttons OFF MAX A/C NORM A/C VENT FLOOR FLOOR/ DEF DEF 1 White Air inlet 2 Yellow Floor/ panel (partial) 3 Red Full floor 4 Blue Panel 5 Black
Source

May 21, 2017 | 2003 Mercury Grand Marquis

1 Answer

Heater control panel doesn't work properly


You are not getting vacuum to the switch or the vacuum motor that switches it on the heater is bad.

Oct 06, 2017 | 1989 Mercury Grand Marquis

2 Answers

I have a mercury mountaineer 2003 V6. It has a problem of making sound repeated when I want to have heat turned on. No sound when the dashboard A.C/Heat stays at AC level, which is the zero? level. The...


When the engine is cold,check the coolant level.

Make sure it's on max.

===

A coolant system should be flush every two years.

===

If you did a coolant flush recently then air pocket can be the cause of the un-even heating problem.

The DIY method is to drive you car onto a ramp or a steep hill.

Iet the engine cool off and top off the coolant tank.

Set MAX heat + MAX fan

Let the engine ran for 20 minutes wih the cap off and the trap air will escape from the coolant reserve tank,

Check coolant level and top off coolant when the engine cools down.



A shop will charge $75+ for this but using an air operated excavate tool!

========

A car with over 90K miles may experience linkage problem to the heater control valve.

The heater control valve (near the firewall) may be stick over time.

Open the hood and move the heater to max and min. Back and forth.

Clean and lube the linkage with WD-40 to free the heater control valve.

If it's a vacuum type heater control valve then cash for leaky vac. hoses.


=======
Move the fan switch back and forth to re-new the electrical conductors.

Pass a vacuum over the control panel to prevent dust build up behind the console.

Sep 13, 2009 | 2003 Mercury Mountaineer

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

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