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Heater/AC blows through defrost

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  #1 (permalink)  
Old 30 Dec 2013, 02:00 pm
Fresh Cruiser
Join Date: Nov 2013
Posts: 17
Default Heater/AC blows through defrost

I've had similar issues on other vehicles but after about 30-40 min the heater or AC will blow only through the defrost when set to blow on vents or what not.

Now, I'm figuring this is a vacuum issue, but I'm wondering if there is a good place to start on this issue? I was figuring the little diaphragm in the engine compartment but any advice would be appreciated.

it's an 2001 pt with 2.4 dohc

I tried to search but didn't have anything worth looking at for results
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Old 30 Dec 2013, 02:45 pm
Obsessed Cruiser
Join Date: Sep 2001
Posts: 27,758
Default Re: Heater/AC blows through defrost

Start here, in the dash. Make sure everything is connected and the vacum hoses are attached.

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Old 30 Dec 2013, 04:24 pm
randyincctx's Avatar
Veteran Cruiser
Join Date: Jun 2013
Location: Corpus Christi,Tx.
Posts: 3,485
Lightbulb Re: Heater/AC blows through defrost

In addition to checking the climate control panel,some of this may help also.....

Here follows a cut and paste from a 2003 shop manual.
The system pulls outside (ambient) air through the cowl opening at the base of the windshield. Then it goes into the plenum chamber above the heater-A/C housing. On air conditioned vehicles, the air passes through the evaporator. Air flow can be directed either through or around the heater core. This is done by adjusting the blend-air door with the TEMP control on the instrument panel. The air flow can then be directed from the panel, floor and defrost outlets in various combinations using the mode selector.
There are 17 different mode selections possible. Air flow velocity can be adjusted with the blower speed selector switch on the instrument panel.
On A/C equipped vehicles the ambient air intake can be controlled by opening and closing the recirculating air door. When placed in RECIRC, air that is inside vehicle is removed continuously and recirculated through unit housing. Ambient air cannot be controlled on vehicles without A/C. The system uses outside air at all times. The air conditioning compressor can be engaged by turning the fan switch counterclockwise from the off position. It can also be engaged by placing the mode control in the mix to defrost positions. This will remove heat and humidity from the air before it is directed through or around the heater core.
All vehicles are equipped with a common heater- A/C housing assembly. The system combines air conditioning, heating, and ventilating capabilities in a single unit housing mounted under the instrument panel. On heater-only systems, the evaporator coil is omitted from the housing and replaced with an air restrictor plate. Outside air enters the vehicle through the cowl top opening at the base of the windshield, and passes through a plenum chamber to the heater-A/C system blower housing. Air flow velocity can then be adjusted with the blower motor speed selector switch on the heater-A/C control panel. The air intake openings must be kept free of snow, ice, leaves, and other obstructions for the heater-A/C system to receive a
sufficient volume of outside air. It is also important to keep the air intake openings clear of debris because leaf particles and other debris
that are small enough to pass through the cowl plenum screen can accumulate within the heater-A/C housing. The closed, warm, damp and dark environment created within the heater-A/C housing is ideal for the growth of certain molds, mildews and other fungi. Any accumulation of decaying plant matter provides an additional food source for fungal spores, which enter the housing with the fresh air. Excess debris, as well as objectionable odors created by decaying plant matter and growing fungi can be discharged into the passenger compartment during heater-A/C system operation.
The heater and optional air conditioner are blend-air type systems. In a blend-air system, a blend-air door controls the amount of unconditioned air (or cooled air from the evaporator on models with air conditioning) that is allowed to flow through, or around, the heater core. A temperature control knob on the heater-A/C control panel determines the discharge air temperature by moving a cable, which operates the blend-air door. This allows an almost immediate manual control of the output air temperature of the system.
The mode control knob on the heater-only or heater- A/C control panel is used to direct the conditioned air to the selected system outlets. The mode control switch uses a cable to control the mode door, while
the recirculation air door is operated by a vacuum actuator motor.
On air conditioned vehicles, the outside air intake can be shut off by selecting the recirculation mode (Recirc) with the mode control knob. This will operate a vacuum actuated recirculating air door that closes off the outside fresh air intake and recirculates the air that is already inside the vehicle.
The optional air conditioner for all models is designed for the use of non-CFC, R-134a refrigerant. The air conditioning system has an evaporator to cool
and dehumidify the incoming air prior to blending it with the heated air. This air conditioning system uses an evaporator probe to maintain minimum evaporator temperature and prevent evaporator freezing, and cycles the compressor clutch.-

The vehicle uses vacuum to operate only the recirculation door. All other controls are cable. When vacuum is supplied to the actuator, the door moves to the Recirculation position. The actuator is spring loaded so the door moves to the Outside-air position when there is no vacuum supplied. The operation of the door can be viewed by removing the blower motor and looking up into the unit inlet.
Normally, vacuum is supplied to the actuator by placing the Circulation control knob in the Recirculation position. The Mode and the circulation control are mechanically interlocked so the circulation control cannot be placed in the RECIRC position if the mode control is at or between the mix and defrost positions. Vacuum is supplied to the actuator only when circulation control is at the RECIRC position. If the circulation control is between the outside air position and RECIRC position the system will be in outside air. If the circulation control is in the RECIRC position and the mode control is moved from the floor to the defrost positions, the circulation control
will move from the RECIRC position, to the outside air position beginning at the mix position. This is to prevent window fogging.
The recirculation door actuator is a vacuum controlled actuator used to control movement of the recirculation door in air conditioner equipped vehicles.
The instrument panel must be removed from the
vehicle to gain access to the recirculation door actuator.
(1) Remove the battery negative cable
(2) Remove instrument panel from vehicle
(3) Disconnect vacuum line harness connector from
the nipple on the recirculation door actuator.
(4) Release the latch that secures the recirculation door actuator mount to the stanchion on the heater- A/C unit housing, and disengage the recirculation door actuator from the housing.
(5) Disconnect the recirculation door actuator linkage
from the recirculation door lever.
(6) Remove the recirculation door actuator from the heater-A/C unit housing.
2003 PT Cruiser (Base-N/A) Patriot Blue Pearl Purchased @ Police Impound Auction for $1,000.
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  #4 (permalink)  
Old 01 Jan 2014, 01:36 pm
Fresh Cruiser
Join Date: Nov 2013
Posts: 17
Default Re: Heater/AC blows through defrost

that last post looks like ripping the whole dash out lol That might could suck, I just changed the head gasket trying to get it back together, figured I could do some of that at the same time
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