DESCRIPTION
| CAUTION | When discharging air conditioning system, use only approved refrigerant recovery/recycling equipment. Make every attempt to avoid discharging refrigerant into the atmosphere. |
The A/C-heater system uses a plate-fin evaporator core with an accumulator/drier, a fixed orifice tube for refrigerant flow control, and a clutch cycling pressure switch to control the cycling of the compressor magnetic clutch. The compressors used in these systems are either FS-6 or 6E171. Both are 6-cylinder swash-plate type compressors. The compressor is driven by a "V" belt. Belt tension is adjusted automatically by means of a tensioner on gasoline engines or by adjusting the bracket and compressor on 7.3L diesel engines.
Two Schrader type service access gauge port valves are used in this system. The high pressure valve is located near the compressor in the discharge line and has a quick disconnect type valve body.
This requires a special high pressure service access valve adapter to connect a manifold gauge set or a charging station to the valve. The other service access gauge port valve is located on the inlet of the suction accumulator and is used to measure evaporator pressure.
The evaporator case, containing the evaporator core, accumulator/drier and blower motor, is attached to the dash panel in the engine compartment. The plenum, containing the heater core, is attached to the dash panel in the passenger compartment.
System air flow is controlled by a vacuum selector valve attached to the control assembly. This valve controls vacuum to operate the vacuum motors and also contains the on-off switch for the blower motor and the clutch circuit. System air temperature is regulated by a temperature blend door controlled by cable from the temperature control lever.
Scheme 1
TEMPERATURE LEVER OPERATION
Temperature is controlled by a cable operated blend-air door in the plenum assembly. When the temperature control lever is in the "COOL" position, all air is directed around the heater core. When the temperature control lever is moved to the "WARM" position, all air is directed through the heater core. When the temperature control lever is between "COOL" and "WARM" positions, air is directed through and around the heater core.
MODE CONTROL LEVER OPERATION
The mode control lever actuates a vacuum selector valve which directs vacuum to vacuum motors within the system to control air source intake and air discharge from the system. The mode selector lever also operates the blower on-off switch and the A/C compressor clutch operating circuit.
The actual cycling of the clutch is dependent on the position of the mode selector lever and the pressure switch in the refrigerant system. Both switches must be closed to energize the clutch for compressor operation.
BLOWER SWITCH OPERATION
Blower speeds are controlled by a 4-position blower switch and a resistor assembly located in the evaporator case upstream from the evaporator core. The switch is used to select low, 2 intermediate or high blower speeds. The blower is tuned off by the mode selector lever when it is in the "OFF" position. This is accomplished by a switch integral with vacuum selector and attached to control assembly.
RESISTOR/THERMAL LIMITER OPERATION
The resistor assembly also contains a thermal limiter which is used as a temperature protecting fuse. The thermal limiter is located a pre-set distance from the resistor coils.
If the temperature of the thermal limiter reaches approximately 250°F (121°C), the limiter contacts will open, interrupting the blower motor circuit for all blower speeds except high speed. The thermal limiter will not reset and the resistor assembly must be replaced if the thermal limiter opens.
Pressure Relief Valve
A pressure relief valve is installed on the compressor to protect system from excessively high pressures. It shuts off power to the magnetic clutch when system pressures exceed 450 psi (31.6 kg/cm 2 )
Fixed Orifice Tube
The fixed orifice tube assembly is the restriction between high and low-pressure liquid refrigerant. It meters the flow of liquid refrigerant into the evaporator core. The diameter of the orifice tube is 0.62" and is Red in color with a White outlet tip. Evaporator temperature is controlled by sensing the pressure within the evaporator with a pressure operated electric switch. The pressure switch controls compressor operation to maintain evaporator pressure a limited amount.
The fixed orifice tube is located in the inlet side of the evaporator tube and has filter screens on the inlet and outlet ends of the tube body. Adjustments or repairs cannot be made to the orifice tube. It must be replaced as a unit with the evaporator inlet tube.
Clutch Cycling Pressure Switch
The clutch cycling pressure switch is mounted on top of the suction accumulator/drier assembly. A Schrader Valve depressor located in the end of the switch presses in on the Schrader Valve stem as the switch is mounted, this allows the suction pressure inside the accumulator/drier canister to control switch operation.
The electrical contacts inside the switch are normally open when suction pressure is approximately 26 psi (1.8 cm/kg(2). Contacts will close and activate the compressor clutch when suction pressure reaches approximately 45 psi (3.2 kg./cm 2 or above. The electrical switch contacts control current to the A/C magnetic clutch. When working properly the cycling clutch switch will control evaporator core pressure at a point where the fin surface of the evaporator will be just above the point of freezing.
TEMPERATURE CONTROL CABLE
- Cable does not normally require adjustment. To check operation, move control lever all the way to the left and then back to the right as far as possible. When released the lever should bounce back slightly.
- If the lever can be moved all the way to either end of the slot without bounce back, the cable should be adjusted by moving cable mounting point.
- Remove glove box. Remove push nut holding cable wire coil on blend-air door crank. Remove the screw attaching cable to plenum.
- Two drill dimples can be seen on cable mounting flange. If lever did not bounce back at "WARM" setting, drill an 11/64" hole in the dimple closest to blend door crank.
- If lever did not bounce back at "COOL" setting, drill the hole in the dimple furthest from the blend door crank. Install the cable using the new hole. Check cable operation. Reinstall glove box.
Scheme 2
- Remove cable jacket from metal attaching clip on bottom of plenum by depressing clip tab and pulling cable down. With cable end attached to door cam and/or crank arm, set function control lever to "DEFROST" position and hold firmly. (Scheme 2)
- With cable end attached to function cam, pull on cable jacket until cam travel stops, install cable into clip, by pushing down until it snaps into place.
TROUBLE SHOOTING & DIAGNOSIS
See the MANUAL A/C SYSTEM article in this section.
Removal
- Disconnect battery ground. Discharge A/C refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect electrical connector from pressure switch. Unscrew pressure switch from accumulator.
- Disconnect suction hose from accumulator and cap hose. Loosen fitting connecting suction accumulator to evaporator core.
- Remove screws attaching 2 straps to mounting bracket. Remove accumulator from evaporator core and remove 2 straps from accumulator.
Installation
To install, reverse removal procedure, using new "O" ring lubricated with clean refrigerant oil. Leak test, evacuate and recharge system.
- Disconnect battery ground. Disconnect blower motor electrical connector. Disconnect blower motor air cooling tube from blower motor. (Scheme 3) Remove 4 blower mounting plate attaching screws.
- Remove motor and wheel assembly from blower housing. Remove hub clamp spring from blower wheel hub and the retainer from motor shaft. Remove wheel from motor shaft.
To install, reverse removal procedure. Position wheel on motor shaft. Cement blower motor air tube on nipple of blower motor housing with adhesive.
Exploded View of Blower Motor and Wheel Assembly Cement blower motor air tube to nipple with adhesive when installing. Scheme 3
Disconnect wire connector from the pressure switch. Unscrew pressure switch from accumulator. To install, use a new "O" ring lubricated with clean refrigerant oil. Screw in switch finger tight only. Check for leaks.
Note. When tightening switch, tighten switches with plastic base finger tight only, and switches with metal base to 5-10 ft. lbs. (7-13 N.m).
COMPRESSOR INFORMATION
Note. F-Series and Bronco vehicles are equipped with one of these engines applications. Determine which engine applies to your vehicle and use that illustration for compressor removal and installation assistance. (Scheme 4)- (Scheme 7).
Scheme 4
Scheme 5
Scheme 6
Scheme 7
- On some compressor applications, the compressor manifolds are a brazed type steel and are an integral part of the hose assembly. On other models, the manifolds are made of extruded aluminum and are attached to the hose assembly with a threaded fitting. (Scheme 3)- (Scheme 6).
- Two different types and colors of "O" rings are used on the compressor manifolds and are not interchangeable. One "O" ring is Black and the other is Red. They must be replaced with "O" rings of exactly the same color. Some vehicles may have Black "O" rings on one manifold and a Red "O" rings on the other manifold.
To Install, lubricate all "O" rings with clean refrigerant oil. Apply Loc-tite to the new manifold mounting bolts and tighten to specification. Leak test, evacuate and recharge system. Check system for proper operation.
CONDENSER
Note. Condenser refrigerant lines are connected with spring-locked couplings which require a special tool (T81P-19623-G) to release spring. Close tool around coupling and push into cage toward condenser. Pull hose away from condenser and unclamp tool from disconnected coupling.
View of Spring Lock Coupling & Tool (T81P-19623-G). Scheme 8
- Discharge refrigerant from system using approved refrigerant recovery/recycling equipment. Disconnect liquid and discharge lines from condenser and cap lines. Drain cooling system. Disconnect upper radiator hose from radiator.
- From under the vehicle, remove 2 screws attaching 2 condenser lower mounting brackets to the front of radiator support. Remove radiator upper retaining brackets.
- Tilt top of radiator rearward and remove 2 screws attaching 2 condenser upper mounting brackets to the rear side of radiator support. Lift condenser from vehicle.
To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil. Leak test, evacuate and recharge system.
- Pull off radio control knobs from control shafts. Remove 2 screws attaching the top of the instrument panel center finish panel to instrument panel pad and remove finish panel. (Scheme 9)
- Remove knobs from control assembly by placing a small screwdriver between knob spring and control panel. Pull on the screwdriver while applying pressure on spring retainer. Pull the knob from the control assembly. Remove ashtray, ashtray bracket and floor register duct.
- Remove 4 control assembly attaching screws. Disconnect wire harness connectors from blower switch, illumination light, vacuum selector switch and auxiliary fuel tank switch or rear window defogger switch (if equipped).
- Disconnect vacuum harness connector from vacuum selector valve. Disengage the mode and temperature cable end retainers from the control panel.
- Remove spring nut attaching temperature control cable to control lever arm. Remove control panel.
To install, reverse removal procedure.
A/C-Heater Control Panel Removal. Scheme 9
- Discharge A/C refrigerant system using approved refrigerant recovery/recycling equipment. Drain coolant from radiator. Disconnect blower motor connector, motor resistance wires and wires connected to the pressure switch.
- Disconnect vacuum supply hose from vacuum reservoir and small vacuum hose from check valve. Reposition check valve away from evaporator case. Disconnect refrigerant line from evaporator and suction line from accumulator and cap lines.
- Disconnect heater hoses from heater core and plug openings. In the passenger compartment, remove 2 screws attaching bottom of evaporator case to the dash panel. Remove screw attaching lower edge of plenum to dash panel.
- Unplug vacuum harness at connector located near the right end of plenum and tuck harness from the recirculation duct to opening back into the opening.
- Remove 2 retaining nuts attaching evaporator case and recirculation duct forward and remove from vehicle. Recirculation duct can be removed from evaporator case by removing 5 rivets.
To install, reverse removal procedure using new "O" rings lubricated with clean refrigerant oil at suction and refrigerant lines.
Evaporator & Plenum Removal. Scheme 10
- Disconnect battery ground. Discharge A/C refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect electrical connector from pressure switch on the side of accumulator. Remove pressure switch from accumulator.
- Disconnect suction and refrigerant hoses from accumulator and cap openings. Remove screw attaching bottom of plenum to dash panel. Remove nut retaining upper left corner of the evaporator case to dash panel.
- Remove 6 screws attaching left evaporator to evaporator case. Remove spring clip holding left side of housing cover plate and left evaporator housing together at dash panel. Remove left evaporator housing from evaporator case. Remove evaporator core and accumulator from evaporator case.
To install, reverse removal procedure, using new "O" rings lubricated with clean refrigerant oil at hose fittings and after installing a new fixed orifice tube as described in this article. Apply a bead of rope sealer (D9AZ-19560-A or equivalent) at flange of evaporator case and evaporator core tubes. Add 3 oz. of clean refrigerant oil to accumulator.
Scheme 11
- Discharge A/C refrigerant system using approved refrigerant recovery/recycling equipment. Disconnect refrigerant line from evaporator core. Lubricate refrigerant and orifice tube "O" rings by pouring small amount of refrigerant oil into refrigerant line. Engage removal tool (Motorcraft YT-1008 or equivalent) with the 2 tangs on fixed orifice tube. NOTE: Do not twist or rotate orifice tube in refrigerant line or breakage may occur. (Scheme 11): Fixed Orifice Tube Removal
- Hold T-handle of tool and run the nut down against refrigerant line until orifice tube is pulled from refrigerant line. If orifice tube breaks in refrigerant line, it must be removed with extractor tool (Motorcraft YT-1009 or T83L-19990-B).
- To remove broken orifice tube, insert screw end of extractor tool into refrigerant line and threaded end of tool into brass tube in center of broken orifice tube. Run tool nut down against refrigerant line, removing orifice tube.
To install orifice tube, use "O" rings lubricated with refrigerant oil. Place the fixed orifice tube in removal tool, and insert fixed orifice tube into evaporator core tube until orifice is seated at stop. Remove tool and reconnect lines. Leak test, evacuate and recharge system.
HEATER CORE
Note. This procedure is for vehicles with air conditioning systems only. For replacement on vehicles equipped with heater systems only, see HEATER SYSTEMS article in this section.
Drain coolant from radiator. Disconnect heater hoses from heater core. Cap heater hoses. Remove glove box liner. Remove 8 screws attaching heater core cover to plenum. Remove cover. Remove heater core from plenum. To install, reverse removal procedure.
