relay FORD FESTIVA 1991 Owner's Manual

Fig. 2: Ignition Primary Trouble Shooting Chart

STARTER TROUBLE SHOOTING
BASIC STARTER TROUBLE SHOOTING CHART
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
Starter Fails to Operate
Dead battery or bad connections between starter and batteryCheck battery charge and all
wires and connections to
starter
Ignition switch faulty or misadjustedAdjust or replace ignition
switch
Open circuit between starter switch ignition terminal on starter relayCheck and repair wires and
connections as necessary
Starter relay or starter defectiveSee Testing in STARTER
article
Open solenoid pull-in wireTesting in STARTER article
Starter Does Not Operate and Headlights Dim
Weak battery or dead cellCharge or replace battery as
necessary
Loose or corroded battery connectionsCheck that battery connections
are clean and tight
Internal ground in starter windingsSee Testing in STARTER
article
Grounded starter fieldsSee Testing in STARTERS
Armature rubbing on poleSee STARTER article shoes
Starter Turns but Engine Does Not Rotate
Starter clutch slippingSee STARTER article
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Broken clutch housingSee STARTER article
Pinion shaft rusted or drySee STARTER article
Engine basic timing incorrectSee Ignition Timing in TUNE-
UP article
Broken teeth on engine flywheelReplace flywheel and check for
starter pinion gear damage
Starter Will Not Crank Engine
Faulty overrunning clutchSee STARTER article
Broken clutch housingSee STARTER article
Broken flywheel teethReplace flywheel and check for
starter pinion gear damage
Armature shaft sheared or reduction gear teeth strippedSee STARTER article
Weak batteryCharge or replace battery as
necessary
Faulty solenoidSee On-Vehicle Tests in
STARTER article
Poor groundsCheck all ground connections
for tight and clean connections
Ignition switch faulty or misadjustedAdjust or replace ignition
switch as necessary
Starter Cranks Engine Slowly
Battery weak or defectiveCharge or replace battery as
necessary
Engine overheatedSee ENGINE COOLING
SYSTEM article
Engine oil too heavyCheck that proper viscosity oil
is used
Poor battery-to-starter connectionsCheck that all between battery
and starter are clean and tight
Current draw too low or too highSee Bench Tests in STARTER
article
Bent armature, loose pole shoes screws or worn bearingSee STARTER article
Burned solenoid contactsReplace solenoid
Faulty starterReplace starter
S t a r t e r E n ga ge s E n gin e On l y M o me n t a r il y
Engine timing too far advancedSee Ignition Timing in TUNE-
UP article
Overrunning clutch not engaging properlyReplace overrunning clutch.
See STARTER article
Broken starter clutchSee STARTER article
Broken teeth on engine flywheelReplace flywheel and check
starter pinion gear for damage
Weak drive assembly thrust springSee STARTER article
Weak hold-in coilSee Bench Tests in STARTER
article
Starter Drive Will Not Engage
Defective point assemblySee Testing in STARTER
article
Poor point assembly groundSee Testing in STARTER
article
Defective pull-in coilReplace starter solenoid
Starter Relay Does Not Close
Dead batteryCharge or replace battery as
necessary
Faulty wiringCheck all wiring and
connections leading to relay
Neutral safety switch faultyReplace neutral safety switch
Starter relay faultyReplace starter relay
Starter Drive Will Not Disengage
Starter motor loose on mountingsTighten starter attach bolts
Worn drive end bushingSee STARTER article
Damaged engine flywheel teethReplace flywheel and starter
pinion gear for damage
Drive yolk return spring broken or missingReplace return spring
Faulty ignition switchReplace ignition switch
Insufficient clearance between winding leads to solenoid terminal and main contact in solenoidReplace starter solenoid
Starter clutch not disengagingReplace starter clutch
Ignition starter switchReplace ignition switch
contacts sticking
Starter Relay Operates but Solenoid Does Not
Faulty solenoid switch, switch connections or relayCheck all wiring between relay
and solenoid or replace relay
or solenoid as necessary
Page 5 of 36 MITCHELL 1 ARTICLE - GENERAL INFORMATION Trouble Shooting - Basic Procedures
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BRAKES
BRAKE SYSTEM TROUBLE SHOOTING
BRAKE SYSTEM TROUBLE SHOOTING CHART
CONDITIONPOSSIBLE CAUSE
Insufficient, Erratic, or No HeatLow Coolant Level
.....Incorrect thermostat.
.....Restricted coolant flow through core.
.....Heater hoses plugged.
.....Misadjusted control cable.
.....Sticking heater control valve.
.....Vacuum hose leaking.
.....Vacuum hose blocked.
.....Vacuum motors inoperative.
.....Blocked air inlet.
.....Inoperative heater blower motor.
.....Oil residue on heater core fins.
.....Dirt on heater core fins.
Too Much HeatImproperly adjusted cables.
.....Sticking heater control valve.
.....No vacuum to heater control valve.
.....Temperature door stuck open.
Air Flow Changes During AccelerationVacuum system leak.
.....Bad check valve or reservoir.
Air From Defroster At All TimesVacuum system leak.
.....Improperly adjusted control cables.
.....Inoperative vacuum motor.
Blower Does Not Operate CorrectlyBlown fuse.
.....Blower motor windings open.
.....Resistors burned out.
.....Motor ground connection loose.
.....Wiring harness connections loose.
.....Blower motor switch inoperative.
.....Blower relay inoperative.
.....Fan binding or foreign object in housing.
.....Fan blades broken or bent.
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
Brakes Pull Left or Right
Incorrect tire pressureInflate tires to proper pressure
Front end out of alignmentSee WHEEL ALIGNMENT
Mismatched tiresCheck tires sizes
Restricted brake lines or hosesCheck hose routing
Loose or malfunctioning caliperSee DISC BRAKES or
BRAKE SYSTEM
Bent shoe or oily liningsSee DRUM BRAKES or
BRAKE SYSTEM
Malfunctioning rear brakesSee DRUM, DISC BRAKES
or BRAKE SYSTEM
Loose suspension partsSee SUSPENSION
Noises Without Brakes Applied
Front linings worn outReplace linings
Dust or oil on drums or rotorsSee DRUM, DISC BRAKES
or BRAKE SYSTEM
Noises With Brakes Applied
Insulator on outboard shoe damagedSee DISC BRAKES or
BRAKE SYSTEM
Incorrect pads or liningsReplace pads or linings
Brake Rough, Chatters or Pulsates
Excessive lateral runoutCheck rotor runout
Parallelism not to specificationsReface or replace rotor
Wheel bearings not adjustedSee SUSPENSION
Rear drums out-of-roundReface or replace drums
Disc pad reversed, steel against rotorRemove and reinstall pad
Excessive Pedal Effort
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GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING
BASIC GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING CHART
Overheating
Coolant LeakFill/Pressure Test System
A/C Condenser Fins CloggedRemove/Clean Condenser
Radiator Fins CloggedRemove/Clean Radiator
Thermostat Stuck ClosedReplace Thermostat
C l o gge d C o o l in g S yst e m P a ssa ge sClean/Flush Cooling System
Water Pump MalfunctionReplace Water Pump
Fan Clutch MalfunctionReplace Fan Clutch
Retarded Ignition TimingReset Ignition Timing
Cooling Fan MalfunctionTest Cooling Fan/Circuit
Cooling Fan Motor MalfunctionTest Fan Motor
Cooling Fan Relay MalfunctionTest Fan Relay
Faulty Radiator CapReplace Radiator Cap
Broken/Slipping Fan BeltReplace Fan Belt
Restricted ExhaustRepair Exhaust System
Corrosion
Impurities In CoolantClean/Flush System
Coolant Leakage
Damaged hoseReplace Hose
Leaky Water PumpReplace Water Pump
Damaged Radiator SeamReplace/Repair Radiator
Leaky Thermostat CoverReplace Thermostat Cover
Cylinder Head ProblemCheck Head/Head Gasket
Leaky Freeze PlugsReplace Freeze Plugs
Recovery System Inoperative
Loose and/or Defective Radiator CapReplace Radiator Cap
Overflow Tube Clogged and/or LeakingRepair Tube
Recovery Bottle Vent RestrictedClean Vent
No Heater Core Flow
Collapsed Heater HoseReplace Heater Hose
Pl u gge d He a t e r C o r eClean/Replace Heater Core
Faulty Heater ValveReplace Heater Valve
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
Engine Lopes At Idle
In t ake man ifo l d -t o -h ead l eaksReplace manifold gasket, See
ENGINES
Blown head gasketReplace head gasket, See
ENGINES
Worn timing gears, chain or sprocketReplace gears, chain or
sprocket
Worn camshaft lobesReplace camshaft, See
ENGINES
Overheated engineCheck cooling system, See
COOLING
Blocked crankcase vent valveRemove restriction
Le a kin g E GR va l veRepair leak and/or replace
va l ve
Faulty fuel pumpReplace fuel pump
Engine Has Low Power
Leaking fuel pumpRepair leak and/or replace
fu el p u mp
Excessive piston-to-bore clearanceInstall larger pistons, See
ENGINES
Sticking valves or weak valve springsCheck valve train components,
See ENGINES
Incorrect valve timingReset valve timing, See
ENGINES
Worn camshaft lobesReplace camshaft, See
ENGINES
Blown head gasketReplace head gasket. See
ENGINES.
Clutch slippingAdjust pedal and/or replace
components, See ENGINES
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VACUUM PUMP DIAGNOSIS
FUEL INJECTION TROUBLE SHOOTING
BASIC FUEL INJECTION TROUBLE SHOOTING CHART
EGR valve malfunctionReplace EGR valve
Blocked or damaged exhaust systemRemove restriction and/or
replace components
Blocked fuel tank filterReplace filter
Restricted fuel filterRemove restriction and/or
replace filter
Block vent in gas capRemove restriction and/or
replace cap
Tank-to-injection pump fuel supply blockedCheck fuel lines and
connections
Blocked fuel return systemRemove restriction
Incorrect or contaminated fuelReplace fuel
Blocked injector nozzlesCheck nozzle for blockage, see
FUEL SYSTEMS
Low compressionCheck valves, rings, pistons,
see ENGINES
Loud Engine Noise With Black Smoke
Basic timing incorrectReset timing, see FUEL
SYSTEMS
EGR valve malfunctionReplace EGR valve
Internal injection pump malfunctionReplace injection pump, see
FUEL SYSTEMS
Incorrect injector pump housing pressureCheck pressure, see FUEL
SYSTEMS
Engine Overheating
Cooling system leaksCheck cooling system and
repair leaks
Belt slipping or damagedCheck tension and/or replace
belt
Thermostat stuck closedRemove and replace
thermostat, see ENGINE
COOLING
Head gasket leakingReplace head gasket
Oil Light on at Idle
Low oil pump pressureCheck oil pump operation, see
ENGINES
Oil cooler or line restrictedRemove restriction and/or
replace cooler
Engine Won't Shut Off
Injector pump fuel solenoid does not return fuel valve to OFF positionRemove and check solenoid
and replace if needed
CONDITION & POSSIBLE CAUSECORRECTION
Excessive Noise
Loose pump-to-drive assembly screwsTighten screws
Loose tube on pump assemblyTighten tube
Valves not functioning properlyReplace valves
Oil Leakage
Loose end plugTighten end plug
Bad seal crimpRemove and re-crimp seal
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
Engine Won't Start (Cranks Normally)
Cold start valve inoperativeTest valve and circuit
Poor connection;vacuum or wiringCheck vacuum and electrical
connections
Contaminated fuelTest fuel for water or alcohol
Defective fuel pump relay or circuitTest relay and wiring
Battery too lowCharge and test battery
Low fuel pressureTest pressure regulator and
fuel pump, check for restricted
lines and filters
No distributor reference pulsesRepair ignition system as
necessary
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Fig. 4: Ignition Primary Trouble Shooting Chart

STARTER TROUBLE SHOOTING
BASIC STARTER TROUBLE SHOOTING CHART
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
Starter Fails to Operate
Dead battery or bad connections between starter and batteryCheck battery charge and all
wires and connections to
starter
Ignition switch faulty or misadjustedAdjust or replace ignition
switch
Open circuit between starter switch ignition terminal on starter relayCheck and repair wires and
connections as necessary
Starter relay or starter defectiveSee Testing in STARTER
article
Open solenoid pull-in wireSee Testing in STARTER
article
Starter Does Not Operate and Headlights Dim
Weak battery or dead cellCharge or replace battery as
necessary
Loose or corroded battery connectionsCheck that battery
connections are clean and
tight
Internal ground in starter windingsSee Testing in STARTER
article
Grounded starter fieldsSee Testing in STARTERS
Armature rubbing on pole shoesSee STARTER article
Page 19 of 36 MITCHELL 1 ARTICLE - GENERAL INFORMATION Trouble Shooting - Basic Procedures
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Starter Turns but Engine Does Not Rotate
Starter clutch slippingSee STARTER article
Broken clutch housingSee STARTER article
Pinion shaft rusted or drySee STARTER article
Engine basic timing incorrectSee Ignition Timing in
TUNE-UP article
Broken teeth on engine flywheelReplace flywheel and check
for starter pinion gear damage
Starter Will Not Crank Engine
Faulty overrunning clutchSee STARTER article
Broken clutch housingSee STARTER article
Broken flywheel teethReplace flywheel and check
for starter pinion gear damage
Armature shaft sheared or reduction gear teeth strippedSee STARTER article
Weak batteryCharge or replace battery as
necessary
Faulty solenoidSee On-Vehicle Tests in
STARTER article
Poor groundsCheck all ground connections
for tight and clean
connections
Ignition switch faulty or misadjustedAdjust or replace ignition
switch as necessary
Starter Cranks Engine Slowly
Battery weak or defectiveCharge or replace battery as
necessary
Engine overheatedSee ENGINE COOLING
SYSTEM article
Engine oil too heavyCheck that proper viscosity
oil is used
Poor battery-to-starter connectionsCheck that all between
battery and starter are clean
and tight
Current draw too low or too highSee Bench Tests in
STARTER article
Bent armature, loose pole shoes screws or worn bearingsSee STARTER article
Burned solenoid contactsReplace solenoid
Faulty starterReplace starter
S t a r t e r E n ga ge s E n gin e On l y M o me n t a r il y
Engine timing too far advancedSee Ignition Timing in
TUNE-UP article
Overrunning clutch not engaging properlyReplace overrunning clutch.
See STARTER article
Broken starter clutchSee STARTER article
Broken teeth on engine flywheelReplace flywheel and check
starter pinion gear for damage
Weak drive assembly thrust springSee STARTER article
Weak hold-in coilSee Bench Tests in
STARTER article
Starter Drive Will Not Engage
Defective point assemblySee Testing in STARTER
article
Poor point assembly groundSee Testing in STARTER
article
Defective pull-in coilReplace starter solenoid
Starter Relay Does Not Close
Dead batteryCharge or replace battery as
necessary
Faulty wiringCheck all wiring and
connections leading to relay
Neutral safety switch faultyReplace neutral safety switch
Starter relay faultyReplace starter relay
Starter Drive Will Not Disengage
Starter motor loose on mountingsTighten starter attach bolts
Worn drive end bushingSee STARTER article
Damaged engine flywheel teethReplace flywheel and starter
pinion gear for damage
Drive yolk return spring broken or missingReplace return spring
Faulty ignition switchReplace ignition switch
Insufficient clearance between winding leads to solenoid terminal and main contact in solenoidReplace starter solenoid
Starter clutch not disengagingReplace starter clutch
Ignition starter switch contacts stickingReplace ignition switch
Starter Relay Operates but Solenoid Does Not
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TUNE-UP TROUBLE SHOOTING - GAS ENGINE VEHICLES
BASIC SPARK PLUG TROUBLE SHOOTING CHARTS
Faulty solenoid switch, switch connections or relayCheck all wiring between
relay and solenoid or replace
relay or solenoid as necessary
Broken lead or loose soldered connectionsRepair wire or wire
connections as necessary
Solenoid Plunger Vibrates When Switch is Engaged
Weak batteryCharge or replace battery as
necessary
Solenoid contacts corrodedClean contacts or replace
solenoid
Faulty wiringCheck all wiring leading to
solenoid
Broken connections inside switch coverRepair connections or replace
solenoid
Open hold-in wireReplace solenoid
Low Current Draw
Worn brushes or weakReplace brushes or brush
springs as necessary
High Pitched Whine During Cranking Before Engine Fires but Engine Fires and Cranks Normally
Distance too great between starter pinion and flywheelAlign starter or check that
correct starter and flywheel
are being used
High Pitched Whine After Engine Fires With Key released. Engine Fires and Cranks Normally
Distance too small between starter pinion and flywheelFlywheel runout contributes
to the intermittent nature
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
Normal Spark Plug Condition
Light Tan or Gray depositsNo Action
Electrode not burned or fouledNo Action
Gap tolerance not changedNo Action
Cold Fouling or Carbon Deposits
Overrich air/fuel mixtureAdjust air/fuel mixture, see
ENGINE PERFORMANCE
section
Faulty chokeReplace choke assembly, see
ENGINE PERFORMANCE
section
Clogged air filterClean and/or replace air filter
Incorrect idle speed or dirty carburetorReset idle speed and/ or clean
carburetor
Faulty ignition wiresReplace ignition wiring
Prolonged operation at idleShut engine off during long
idle
Sticking valves or worn valve guide sealsCheck valve train
Wet Fouling or Oil Deposits
Worn rings and pistonsInstall new rings and pistons
Excessive cylinder wearRebore or replace block
Excessive valve guide clearanceWorn or loose bearing
Gap Bridged
Deposits in combustion chamber becoming fused to electrodeClean combustion chamber of
deposits
Blistered Electrode
Engine overheatingCheck cooling system
Wrong type of fuelReplace with correct fuel
Loose spark plugsRetighten spark plugs
Over-advanced ignition timingReset ignition timing see
ENGINE PERFORMANCE
Pre-Ignition or Melted Electrodes
Incorrect type of fuelReplace with correct fuel
Incorrect ignition timingReset ignition timing see
ENGINE PERFORMANCE
Burned valvesReplace valves
Engine OverheatingCheck cooling system
Wrong type of spark plug, too hotReplace with correct spark
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FUEL INJECTION TROUBLE SHOOTING
Se ve r a l High F ir in g Lin e s
Fuel Mixture UnbalancedCheck Fuel System
EGR Valve Stuck OpenClean/Replace EGR
Valve
High Plug Wire ResistanceReplace Plug Wire
Cracked/Broken PlugsReplace Plugs
Intake Vacuum LeakRepair Leak
Several Low Firing Lines
Fuel Mixture UnbalancedAdjust Fuel Mixture
Plug Wires ArcingReplace Plug Wires
Cracked Coil ArcingReplace Coil
Uneven CompressionCheck/Repair Engine
Faulty Spark PlugsReplace Plugs
Cylinders Not Firing
Cracked Distributor CapReplace Cap
Shorted Plug WiresReplace Plug Wires
Mechanical Engine FaultCheck/Repair Engine
Spark Plugs FouledReplace Plugs
Carbon Track in Distributor CapReplace Cap
Hard Starting
Defective Ignition Coil(s)Replace Coil(s)
Fouled Spark PlugsReplace Plugs
Incorrect TimingReset Ignition Timing
NOTE:T his article is generic in nature and all inform ation does not apply to all vehicles. For vehicle specific
inform ation, see the appropriate articles in the ENGINE PERFORMANCE category.
Problem & Possible CauseAction
Cold Start Valve InoperativeTest Cold Start Valve
Poor Vacuum/Electrical ConnectionRepair Connections
Contaminated FuelTest Fuel for Water/Alcohol
Bad Fuel Pump Relay/CircuitTest Relay/Wiring
Battery Voltage LowCharge/Test Battery
Low Fuel PressureTest Press. Regulator/Pump
No Distributor Reference PulseRepair Ignition System
Coolant Temp. Sensor DefectiveTest Temp. Sensor/Circuit
No Power To InjectorsCheck Injector Fuse/Relay
Hard Starting
Defective Idle Air Control (IAC)Test IAC and Circuit
EGR Valve OpenTest EGR Valve/Control
Circuit
Restricted Fuel LinesInspect/Replace Fuel Lines
Poor MAP Sensor SignalTest MAP Sensor/Circuit
Engine Stalls During Parking ManeuverCheck P.S. Press. Switch
Rough Idle
Dirty Fuel InjectorsClean/Replace Injectors
Poor MAP Sensor SignalTest MAP Sensor/Circuit
Intermittent Fuel Injector OperationCheck Harness Connectors
Erratic Vehicle Speed Sensor InputsHarness Too Close to Plug
Wires
Poor O2 Sensor SignalTest O2 Sensor/Circuit
Faulty PCV SystemCheck PCV Valve and
Hoses
Poor Acceleration
Weak Fuel PumpReplace Fuel Pump
Dirty Fuel InjectorsClean/Replace Injectors
Excessive Intake Valve DepositsClean Intake System
Poor High Speed Operation
Low Fuel Pump VolumeFaulty Fuel Pump/Filter
Poor MAP Sensor SignalTest Speed Sensor/Circuit
Acceleration Ping/Knock
Faulty EGR SystemCheck EGR Valve and
Hoses
Poor Knock Sensor SignalTest Knock Sensor/Circuit
Poor Baro Sensor SignalTest Baro Sensor/Circuit
Improper Ignition TimingAdjust Timing
Engine OverheatingCheck Cooling System
Poor Quality FuelUse Different Fuel
Carbon Build-UpDecarbon Engine
Page 2 of 3 MITCHELL 1 ARTICLE - GENERAL INFORMATION TROUBLE SHOOTING
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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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