instrument panel FORD FESTIVA 1991 Owner's Manual
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Page 147 of 454

ELECTRONIC CONTROL ASSEMBLY (ECA)
REMOVAL & INSTALLATION
Disconnect negative battery cable. On Festiva, from under instrument panel, remove heater duct. On Capri, disengage push-pin retainers by
pulling back on front edges of both center carpet panels. Remove carpet panel retaining screws and panels. Disconnect ECA wire harness
connector. Remove ECA bolts and ECA. To install, reverse removal procedure. On Festiva, ensure mounting clip is inserted into bulkhead
recess.
FUEL SYSTEM
FUEL SYSTEM PRESSURE RELEASE
Remove rear seat assembly. With engine running, disconnect fuel pump connector. Run engine until it stalls to relieve fuel line pressure.
FUEL INJECTORS
Removal
Relieve fuel system pressure. On Capri, remove throttle body. On Festiva, remove intake plenum. See INTAKE PLENUM. Remove fuel inlet
and fuel return line from fuel rail. Remove electrical connectors from injectors. Remove pressure regulator. See Fig. 4
. Remove fuel rail
attaching bolts and fuel rail. Remove fuel injectors.
Installation
Install NEW "O" rings on fuel injectors and lubricate with gasoline. Install fuel injectors into cylinder head. Install fuel rail onto fuel injectors.
Install fuel rail attaching bolts. To complete installation, reverse removal procedure. Check system for leaks.
Fig. 4: Exploded View of Fuel Control System
Courtesy of FORD MOTOR CO.
FUEL PUMP
Removal
Remove fuel tank sending unit. Remove fuel filter from pump. Remove fuel pump wires from sending unit. Remove retaining clamp screw and
clamp. Remove rubber retaining band (if equipped). Remove fuel pump from sending unit.
Installation
To install, reverse removal procedure. Check system for leaks.
INTAKE PLENUM WARNING:ALWAYS relieve fuel pressure before disconnecting any fuel injection-related com ponent. DO NOT
allow fuel to contact engine or electrical com ponents.
WARNING:ALWAYS relieve fuel pressure before disconnecting any fuel-related com ponent. DO NOT allow fuel to
contact engine or electrical com ponents.
Page 3 of 5 MITCHELL 1 ARTICLE - N - REMOVE/INSTALL/OVERHAUL 1991 ENGINE PERFORMANCE Ford/Mercury Removal, O
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CLEARING CODES
Clearing Codes Procedure
Disconnect negative battery cable. Press brake pedal for 5-10 seconds. Turn off VOM or Super Star II tester. Reconnect battery.
ECA LOCATION
ECA is located on center console behind kick panel on Capri, and under instrument panel on driver side of Festiva.
QUICK TESTS
KEY ON, ENGINE OFF (KOEO) SELF-TEST
KOEO
1. This is a test of electronic engine control system, conducted with power (voltage) applied and engine not running. Activate self-test, and
record all codes displayed.
2. Erase codes, and repeat self-test. Diagnose only codes occurring during repeat self-test. See TROUBLE CODE DEFINITION
table. If
no codes are present, proceed to KEY ON, ENGINE RUNNING (KOER) SELF
-TEST .
KEY ON, ENGINE RUNNING (KOER) SELF-TEST
KOER
1. Deactivate self-test. Start and run engine at 2000 RPM for 2 minutes to warm up EGO sensor. Turn off engine and wait 10 seconds.
2. Restart engine, and activate self-test. Record all service codes displayed. See TROUBLE CODE DEFINITION
table. If no codes are
present, proceed to SWITCH MONITOR TEST
.
SWITCH MONITOR TEST
This test procedure checks input signals received by ECA from individual switches. Use following procedure to perform switch monitor test:
Turn engine off and allow it to cool.
Ensure all accessories are turned off.
Deactivate self-test.
Ensure transmission is in Neutral or Park.
Turn ignition on.
SUPER STAR II Tester
Connect Super Star II tester adapter cable. Turn on tester. Latch center button. Operate each switch listed in SWITCH MONITOR TEST
table. Note output of LED on adapter cable as each switch operates. Record test results.
VOM
1. Ground STI connector. Connect VOM positive lead to SML terminal on self-test connector. Connect negative lead to ground. See Fig.
1 .
2. Operate each switch listed in SWITCH MONITOR TEST
table. Note output on VOM as each switch is operated. Go to specified
PINPOINT TEST if any switch does not meet specification.
SWITCH MONITOR TEST
(1)Festiva only.
(2)Capri only.
NOTE:DO NOT m ove throttle during KOEO self-test.
NOTE:It is necessary to clear codes in m em ory before perform ing this test. DO NOT m ove throttle during test.
NOTE:All switches m ust be tested individually. Allowing a switch to rem ain on while testing another will lead
to false test results.
NOTE:DO NOT m ove throttle, clutch, or transm ission lever unless so directed.
SwitchVOM Indication/Condition(1) Pinpoint Test
A/C SwitchLess Than 1.5 Volts; A/C & Blower Switch OnSTG
Blower Motor SwitchLess Than 1.5 Volts; Switch Set To "2" Or HigherSTG
Brake On/Off SwitchLess Than 1.5 Volts; Brake Pedal Partially
PressedSTP
Clutch Engage/Neutral Gear Switch (2) Less Than 1.5 Volts; In Gear, Clutch ReleasedSTG
Coolant Temperature SwitchLess Than 1.5 Volts; Cooling Fan OnSTP
Defrost SwitchLess Than 1.5 Volts; Defrost Switch OnSTP
Headlight SwitchLess Than 1.5 Volts; Headlight Switch OnSTP
Id l e Swit chLess Than 1.5 Volts; Accelerator Pedal PressedSTG
Page 4 of 20 MITCHELL 1 ARTICLE - G - TESTS W/CODES 1991-92 ENGINE PERFORMANCE Ford Motor Co. Self-Diagnostics
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Page 191 of 454

Back To Article
E - T HEORY/OPERAT ION
1991 ENGINE PERFORMANCE Ford/Mercury T heory & Operation
INTRODUCTION
This article covers basic description and operation of engine performance-related systems and components. Read this article before attempting
to diagnose systems with which you are not completely familiar.
COMPUTERIZED ENGINE CONTROLS
An electronic Control Assembly (ECA) receives and processes signals from various sensors and switches. See Fig. 1 . It then generates signals
which control ignition timing, fuel injection functions and various emission control devices. The ECA has system diagnostic capabilities and
will store trouble codes for use by service technicians.
Fig. 1: Identifying Input Devices & Output Signals (Not All Shown)
Courtesy of FORD MOTOR CO.
ELECTRONIC CONTROL ASSEMBLY (ECA)
The ECA is located under the instrument panel on the driver side. It receives and processes data from sensors, switches and other components.
The ECA generates output signals to control fuel injection, spark timing, other engine functions and emission systems.
CEC INPUT DEVICES
Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To determine input device usage of
a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The available input devices include the following:
BAROMETRIC PRESSURE SENSOR (BP)
This device senses changes in barometric pressure. The ECA uses this information in calculating fuel metering, ignition timing and idle speed.
On Festiva, BP is incorporated into the ECA. On Capri, BP is located on the passenger-side cowl.
BRAKE ON-OFF (BOO) SWITCH
This switch, located at the brake pedal, senses brake operation. The ECA uses this information in calculating fuel metering.
NOTE:Com ponents are grouped into 2 categories. T he first category is CEC INPUT DEVICES, which control or
produce voltage signals m onitored by the control unit. T he second category is CEC OUT PUT SIGNALS,
which are com ponents controlled by the control unit.
Page 1 of 6 MITCHELL 1 ARTICLE - E - THEORY/OPERATION 1991 ENGINE PERFORMANCE Ford/Mercury Theory & Operation
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Page 194 of 454

located under the center of the instrument panel, between the panel and the floor.
Fig. 4: Electric Fuel Pump System Schematic
Courtesy of FORD MOTOR CO.
FUEL PRESSURE REGULATOR
The fuel pressure regulator is located at the fuel return end of the fuel rail and maintains fuel pressure within the fuel rail at a constant 36.3 psi
(2.54 kg/cm
2 ) higher than intake manifold pressure.
FUEL PRESSURE REGULATOR CONTROL SOLENOID (PRC) (CAPRI)
This device closes the vacuum supply to the fuel pressure regulator on hot starts, thus increasing fuel pressure within the fuel rail and
preventing fuel percolation which could cause hard starts during hot conditions. The PRC is located on the cowl panel, next to the canister
purge solenoid.
FUEL PUMP SHUT-OFF (INERTIA) SWITCH
The fuel pump shut-off switch is connected in series with the fuel pump and prevents fuel pump operation in the event of major collision or
vehicle rollover. A reset button is provided to reset the switch after it has been triggered. See Fig. 5
.
Fig. 5: Locating Inertia Switch Reset Button
Courtesy of FORD MOTOR CO.
FUEL CONTROL SYSTEM
ELECTRONIC FUEL INJECTION (EFI)
The ECA receives a signal from the CPS (Festiva) or CID (Capri) for basic fuel injector timing. Signals to the ECA from other sensors and
switches affect injector on-time. The amount of fuel injected is determined by the duration of the electronic pulse sent to the fuel injector from
the ECA.
Between idle and 5000 RPM, fuel is supplied by providing one injection per crankshaft rotation (2 injections per cycle) to all cylinders. There
is one injection per 2 crankshaft rotations when engine speed exceeds 5000 RPM. When engine speed exceeds 6400 RPM, fuel injectors are
shut off to prevent engine damage.
Page 4 of 6 MITCHELL 1 ARTICLE - E - THEORY/OPERATION 1991 ENGINE PERFORMANCE Ford/Mercury Theory & Operation
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Page 206 of 454

High Performance
HSC
High Swirl Combustion
HSO
High Specific Output
HTR
Heater
Hz
Hertz (Cycles Per Second)
"I"
IAC
Idle Air Control
IACV
Idle Air Control Valve
IAT
Intake Air Temperature
IC
Integrated Circuit
ID
Identification
I.D.
Inside Diameter
Ign.
Ignition
IMRC
Intake Manifold Runner Control
In.
In ch es
INCH Lbs.
Inch Pounds
in. Hg
Inches of Mercury
Inj.
Injector
IP
Instrument Panel
ISC
Idle Speed Control
IVSV
Idle Vacuum Switching Valve
Page 8 of 15 MITCHELL 1 ARTICLE - GENERAL INFORMATION Commonly Used Abbreviations
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SUSPENSION TROUBLE SHOOTING
BASIC SUSPENSION TROUBLE SHOOTING CHART
article
Shroud or housing looseTighten holding screws
Lock plate retaining ring not seatedSee STEERING COLUMN
article
Loose sight shieldTighten holding screws
High Steering Shaft Effort
Co l u mn assemb l y misal ign edSee STEERING COLUMN
article
Improperly installed dust shieldAdjust or replace
Tight steering universal jointSee STEERING COLUMN
article
High Shift Effort
Column is out of alignmentSee STEERING COLUMN
article
Improperly installed dust shieldAdjust or replace
Seals or bearings not lubricatedSee STEERING COLUMNS
article
Mounting bracket screws too longReplace with new shorter
screws
Burrs on shift tubeRemove burrs or replace tube
Lower bowl bearing assembled wrongSee STEERING COLUMN
article
Shift tube bent or brokenReplace as necessary
Improper adjustment of shift leversSee STEERING COLUMN
article
Improper Trans. Shifting
Sheared shift tube jointReplace as necessary
Sheared lower shaft leverReplace as necessary
Improper shift lever adjustmentSee STEERING COLUMN
article
Improper gate plate adjustmentSee STEERING COLUMN
article
Excess Play in Column
Instrument panel bracket bolts looseTighten bolts and check
bracket
Broken weld nut on jacketSee STEERING COLUMN
article
Instrument bracket capsule shearedSee STEERING COLUMN
article
Column bracket/jacket bolts looseTighten bolts and check
bracket
Steering Locks in Gear
Release lever mechanismSee STEERING COLUMN
article
NOTE:This is GENERAL inform ation. This article is not intended to be specific to any unique situation or
individual vehicle configuration. T he purpose of this T rouble Shooting inform ation is to provide a list
of com m on causes to problem sym ptom s. For m odel-specific T rouble Shooting, refer to SUBJECT ,
DIAGNOST IC, or T EST ING articles available in the section(s) you are accessing.
CONDITION & POSSIBLE CAUSECORRECTION
Front End Noise
Loose or worn wheelSee Wheel Bearing
Adjustment in SUSPENSION
Worn shocks or shock mountingsReplace struts or strut
mo u n t in gs
Worn struts or strut mountingsReplace struts or strut
mo u n t in gs
Loose or worn lower control armSee SUSPENSION
Loose steering gear-to-frame boltsSee STEERING
Worn control arm bushingsSee SUSPENSION
Ball joints not lubricatedLubricate ball joints & see
Ball Joint Checking in
SUSPENSION
Front Wheel Shake, Shimmy, or Vibration
Tires or wheels out of balanceCheck tire balance
Incorrect wheel alignmentSee WHEEL ALIGNMENT
Drive shaft unbalancedCheck drive shaft balance
Loose or worn wheel bearingsSee WHEEL ALIGNMENT
Loose or worn tie rod endsSee SUSPENSION
Page 34 of 36 MITCHELL 1 ARTICLE - GENERAL INFORMATION Trouble Shooting - Basic Procedures
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Page 345 of 454

Back To Article
HEAT ER SYST EM
1990-92 HEAT ER SYST EMS Ford Motor Co.
DESCRIPTION
The heater system consists of control panel, blower case, heater case, air control doors and ducts. The control panel incorporates 3 control
levers and a 3-speed fan switch. The control panel is located in the center of the instrument panel. All air control doors are cable operated
from the control panel.
The blower case is mounted on the bulkhead, behind the instrument panel on passenger's side of vehicle. The blower case houses a blower
motor, blower motor resistor and the fresh/recirculation air door. The heater case contains mode select door, temperature air mix door and
heater core.
OPERATION
Three control levers, temperature mix, fresh/recirculation and mode select, mechanically operate their associated cables and doors. The
temperature control lever adjusts the mix of fresh or recirculated air with heated air. In full heat position, all airflow goes through the heater
core.
In full cool position, the mix air door closes, allowing airflow to by-pass the heater core. The mode select lever, directs airflow to selected
vents. The fresh/recirculation control lever allows selection of fresh (outside) air or recirculated compartment air.
AJUSTMENT
FRESH/RECIRCULATION CONTROL CABLE
Remove the glove box. Remove fresh/recirculation cable retaining clip. Move control lever to RECIRCULATION position, while holding the
lever door in RECIRCULATION position. Ensure control lever does not move. Install fresh/recirculation cable retaining clip.
MODE SELECT CABLE
Remove mode select cable retaining clip. Move mode select lever to VENT position. Hold mode select lever downward against its stop.
Ensure that mode select lever does not move. Install mode select cable retaining clip.
TEMPERATURE CONTROL CABLE
Set temperature control lever to maximum cold position. Remove temperature cable retaining clip. Hold temperature control lever upward and
against its stop. Ensure that temperature lever does not move. Install temperature cable retaining clip.
TROUBLE SHOOTING
BLOWER MOTOR INOPERATIVE
Check blown motor fuse. Check for defective blower motor and/or blower motor resistor. Check blower motor switch. Check for open in
ground wire. Check for loose electrical connectors or poor connections. See WIRING DIAGRAMS
in this article.
BLOWER DOES NOT CHANGE SPEED
Check for defective blower motor. Check blower motor wiring harness. Check blower motor resistor. Check for blower motor fan switch. See
WIRING DIAGRAMS
in this article.
BLOWER RUNS CONSTANTLY
Check for defective blower motor resistor. Check for short in blower switch or wiring. See WIRING DIAGRAMS
in this article.
HEATER TEMPERATURE INSUFFICIENT
Check for proper coolant level. Check water pump for noise, leaks or wear. Check heater hoses for leaks or restrictions. Check heater core for
leaks, plugs or restrictions. Check inlet and outlet heater hoses for hot water flow. Check thermostat condition and operation. Check air mix
door position and adjust cable if necessary.
IMPROPER WARM AIR DISTRIBUTION
Check air mix door position. Adjust cable as necessary. Check function control door position. Adjust cable as necessary. Check for restriction
in ventilation air duct assembly. Repair as necessary.
TESTING BLOWER MOTOR & RESISTOR
1. Ensure 15-amp blower motor fuse is okay. Using voltmeter, check for battery voltage at blower motor Blue/Yellow terminal. If battery
voltage is present, go to next step. If battery voltage is not present, repair open in Blue/Yellow wire between blower motor and fuse box.
2. Disconnect blower motor connector. Using a jumper wire, apply battery voltage to Blue/Yellow terminal and ground the Blue/Red
terminal. If blower motor does not run, replace blower motor. If blower motor runs, go to next step.
3. Reconnect blower motor connector. Turn ignition on. Turn blower motor off. Disconnect the blower motor resistor connector. Using a
voltmeter, measure voltage at Blue/Red terminal of resistor connector. If battery voltage is not present, repair open in Blue/Red wire
between resistor and blower motor. If voltage is present, go to next step.
4. Using a jumper wire, ground Blue/Black, Blue/Yellow and Blue/White terminals of the blower fan switch one at a time. If the motor
runs at 3 different speeds, go to next step. If not, repair open in wire that failed to operate blower motor.
Page 1 of 4 MITCHELL 1 ARTICLE - HEATER SYSTEM 1990-92 HEATER SYSTEMS Ford Motor Co.
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5. Check blower motor fan switch continuity. Resistance should not exceed 4 ohms. See BLOWER MOTOR FAN SWITCH
CONTINUITY table. If continuity is not present, replace fan switch. If continuity is okay, repair open in Black wire from blower motor
switch to ground.
BLOWER MOTOR FAN SWITCH CONTINUITY
REMOVAL & INSTALLATION
CONTROL PANEL
1. Remove bezel screws and accessory bezel. Remove radio. Remove 4 screws securing control panel to instrument panel. Remove glove
box attaching screws and glove box. Remove the retaining clip and disconnect fresh/recirculation air door cable from mode door lever.
2. Disconnect mode select cable at mode control door lever. Disconnect temperature control cable at temperature control mode door lever.
Pull control panel away from instrument panel. Disconnect blower motor switch connector. Disconnect illumination electrical
connector. Remove control panel. To install, reverse removal procedure. Adjust control cables. See ADJUSTMENTS in this article.
BLOWER MOTOR FAN SWITCH
Remove control panel. See CONTROL PANEL R & I
. Remove blower motor fan switch knob. Remove attaching nut. To install, reverse
removal procedure.
HEATER CORE
1. Disconnect negative battery cable. Remove steering wheel by prying out center trim insert and removing steering wheel retaining nut.
Remove 2 steering wheel cover retaining screws and remove cover. Using a steering wheel puller, remove steering wheel.
2. Remove 5 screws and remove lower and upper steering column covers. Disconnect electrical connections and remove multifunction
switch. Remove 5 screws and pull instrument cluster hood rearward. Disconnect electrical connections and remove instrument cluster
hood.
3. Disconnect speedometer cable at transaxle. Remove 4 instrument cluster screws. Pull instrument cluster rearward and disconnect
speedometer cable and electrical connections. Remove instrument cluster.
4. Remove 2 center bracket mounting bolts under steering column and remove bracket. Remove glove box attaching screws and remove
glove box. Remove left and right heater ducts. Remove fuse panel cover. Remove 2 screws securing fuse panel and push fuse panel
inward. DO NOT remove fuse panel.
5. Slide both seats to most forward position. Remove 2 console attaching screws, located in front of seat belt anchors. Slide both seats to
rearmost position. Remove parking brake console insert. Using a Phillips screwdriver, remove push retainer insert, located at front lower
edge of parking brake console. Pull back on parking brake lever and remove parking brake console.
6. Remove gearshift knob. Remove screws and remove shift console. Remove radio/heater control panel bezel screws and remove bezel.
Remove 4 radio attaching screws. Pull radio out and disconnect antenna lead and electrical connections. Disconnect radio ground lead
and remove radio.
7. Remove 4 screws attaching heater control panel. Disconnect control cables and electrical connections. Remove control panel, while
pulling cables through opening.
8. Pry out bolt cover trim inserts in top corners of dash. Remove bolts located under trim panels. Remove 7 instrument panel attaching
bolts and 2 nuts. Pull instrument panel rearward. Disconnect any harness connectors and clips. Remove instrument panel.
9. Disconnect electrical connections at blower and resistor. Remove harness from routing brackets on heater box. Loosen clamp screw
securing air inlet housing. Remove attaching nuts at top and bottom of heater box. Disconnect defroster ducts and remove heater
assembly.
10. Disconnect link connecting 2 defroster doors. Remove attaching screw just above and to right of blower resistor. Turn heater assembly
around and remove screw just to left of blower motor opening. Remove clips securing 2 halves of heater assembly. Separate halves. Lift
out heater core.
11. To install, reverse removal procedure. Ensure all heater control cables are routed and adjusted properly. See ADJUSTMENTS in this
article. Fill cooling system. Check for leaks.
BLOWER MOTOR & RESISTOR
Disconnect negative battery cable. Remove instrument panel spacer brace located below steering column. Remove airflow duct below steering
column. Disconnect blower motor or resistor wiring. Remove 3 blower motor attaching screws or 2 resistor attaching screws and remove
component. To install, reverse removal procedure.
Switch PositionContinuity Between Wire Colors
1Black-to-Blue/White
2Black-to-Blue/Yellow & Blue/Yellow-to-Blue/Red
3Black-to-Blue/Black & Blue/Black-to-Blue/Red
Page 2 of 4 MITCHELL 1 ARTICLE - HEATER SYSTEM 1990-92 HEATER SYSTEMS Ford Motor Co.
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Page 350 of 454

Fig. 2: Identifying A/C
-Heater Air Distribution Components
Courtesy of FORD MOTOR CO.
OPERATION
A/C-HEATER CONTROL PANEL
The A/C-heater panel is located in the center of instrument panel above the radio. Air discharge outlets are located above, below, in center
and on both sides of instrument panel. The climate control panel consists of 3 slide levers, one A/C on-off push button and a rotary blower
switch.
The lower slide lever is used to control temperature. Sliding lever from far left side (cool) to far right side (warm) increases interior
temperature. The middle slide lever selects fresh air from outside or recirculated air from inside. The upper slide lever controls air delivery
mode. A/C push-button on-off switch activates air conditioning system.
THERMOSTATIC SW ITCH
With A/C system operating, thermostatic switch determines A/C compressor clutch on-time. Control is accomplished by a cable attached
between the temperature blend lever and thermostatic switch. The thermostatic switch sensing tube is installed into (or near) evaporator fins.
Switch is wired in series with A/C relay and Electronic Control Assembly (ECA). The ECA calculates compressor on-time based on A/C relay
signals. This controls evaporator temperature to regulate cool air entering vehicle.
THERMOSTATIC EXPANSION VALVE
The Thermostatic Expansion Valve (TXV) is a controlling device metering liquid refrigerant from high pressure line into evaporator. It also
provides for complete vaporization of all refrigerant entering evaporator.
The high refrigerant pressure is reduced before entering evaporator by a ball valve within TXV. Depending on pressure applied to TXV
diaphragm from both sides of system, TXV allows more or less high pressure refrigerant to be discharged through its orifice into evaporator.
See Fig. 3
.
Page 2 of 14 MITCHELL 1 ARTICLE - 1991 AIR CONDITIONING & HEAT MANUAL A/C
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Page 353 of 454

Fig. 5: Adjusting Recirculated/Fresh Air Door Cable
Courtesy of FORD MOTOR CO.
MODE SELECTOR CABLE
1. Remove air distribution plenum and instrument panel brace. See AIR DISTRIBUTION PLENUM
under REMOVAL &
INSTALLATION. Release cable retaining clip. See Fig. 6
.
2. Move control knob to vent position. While holding lever downward against stop, secure cable using retaining clip.
3. Disconnect defrost door link at defrost door lever. While holding defrost door upward against its stop, adjust defrost door link to a free
fit in defrost door lever. Install air distribution duct. Install instrument panel brace.
Fig. 6: Adjusting Mode Select Cable
Courtesy of FORD MOTOR CO.
TROUBLE SHOOTING
COMPRESSOR CLUTCH TROUBLE CHARTS
Fig. 7: Compressor Clutch Trouble Chart CC1
Courtesy of FORD MOTOR CO.
NOTE:Use the following trouble shooting charts to diagnose air conditioning system problem s.
Page 5 of 14 MITCHELL 1 ARTICLE - 1991 AIR CONDITIONING & HEAT MANUAL A/C
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