ECU MAZDA MIATA 1991 Factory User Guide

Blower motor relay supplies power to blower motor. Blower resistor determines blower speed. With blower
switch in highest position, blower motor is grounded through blower switch. With blower switch in all other
positions, blower motor is grounded through blower resistor and blower switch.
Circuit through compressor clutch is completed when A/C relay is energized and pressure switch is closed. A/C
relay is energized when Engine Control Unit (ECU) unit grounds the solenoid circuit of the relay. The ECU
energizes A/C relay if evaporator thermoswitch is closed and A/C and blower switches are on. The ECU also
controls A/C relay operation according to engine load.
ADJUSTMENTS
AIRFLOW MODE DOOR
Set airflow mode control lever to vent position. Disconnect control cable at airflow mode door lever. Extend
airflow mode door lever until it stops, and hold it there. See Fig. 1
. Attach control cable to door lever and clip.
Ensure control lever moves freely between defrost and vent positions.
AIR-MIX (TEMPERATURE BLEND) DOOR
Set temperature control lever to maximum hot position. Disconnect control cable at air-mix door lever. See Fig.
1 . Extend air-mix door lever until it stops, and hold it there. Attach control cable to door lever and clip. Ensure
control lever moves freely between hot and cold positions.
RECIRCULATED/FRESH AIR DOOR
Set recirculated/fresh air control lever to fresh position. Disconnect control cable at recirculated/fresh air door
lever. Retract recirculated/fresh air door lever until it stops, and hold it there. Attach control cable to door lever
and clip. Ensure control lever moves freely between recirculated air and fresh air positions.
TESTING
AIR BAG WARNING
BLOWER MOTOR CIRCUIT
1. Check 30-amp HEATER circuit breaker in passenger compartment fuse panel. If Red button has not
popped out, go to next step. If Red button has popped out, repair short circuit and press Red button to
reset circuit breaker.
2. Turn ignition on. Turn blower switch to 4th position (high). Check voltage at Blue wire terminal of 2-
wire blower motor connector on bottom of blower case. If no voltage is present, repair wiring between
circuit breaker and blower motor. WARNING:To avoid injury from accidental air bag deployment, read and carefully
follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR
BAG SYSTEM procedures in AIR BAG article in the
ACCESSORIES/SAFETY EQUIPMENT Section.

1991 Mazda MX-5 Miata
A/C-HEATER SYSTEM - MANUAL 1990-92 Manual A/C-Heater Systems
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8. If battery voltage is present, check voltage at Blue/Black wire terminal of A/C relay connector. If no
voltage is present, replace A/C relay. If battery voltage is present, check Engine Control Unit (ECU)
terminal voltage.
9. Turn ignition off. Disconnect pressure switch connector. Check continuity between switch terminals. If
there is continuity, repair circuit between A/C relay and compressor clutch.
10. If there is no continuity, connect manifold pressure gauges to system. If low pressure is 21-43 psi (1.5-3.0
kg/cm
2 ) and high pressure is 171-235 psi (12.0-16.5 kg/cm2 ), replace pressure switch. If pressures are
not as specified, check refrigerant system for proper charge.
CONDENSER (ADDITIONAL) FAN CIRCUIT
1. Turn ignition on. Turn A/C and blower switches on. Check voltage at Black/Blue wire terminal of
condenser fan connector. If no voltage is present, repair circuit between A/C relay and condenser fan.
2. If battery voltage is present, check voltage at Black wire terminal of condenser fan connector. If no
voltage is present, replace condenser fan motor. If battery voltage is present, repair circuit between
condenser fan and ground.
A/C & BLOWER SWITCH
With switches in positions indicated, check continuity between specified terminals of A/C and blower switch
connector. See Fig. 1
. If continuity is not as specified, replace A/C and blower switch.

1991 Mazda MX-5 Miata
A/C-HEATER SYSTEM - MANUAL 1990-92 Manual A/C-Heater Systems
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drive axle lock nut. Check axial play. See WHEEL BEARING under ADJUSTMENTS & INSPECTION.
STRUT ASSEMBLY
Removal & Disassembly
1. Raise vehicle and remove fuel tank filler pipe protector. Remove rear wheel assembly. Remove stabilizer
bar nut and bolt. Remove 2 upper strut mount-to-body nuts. Remove lower strut bolt. Loosen upper and
lower arm bolts. Lower arms and remove strut assembly.
2. Clamp strut securely in soft-jawed vise. Compress coil spring. Remove lock nut and washer. Remove
remaining components and note order for reassembly.
Inspection
Check strut for leaks or abnormal noise. Inspect parts for wear or damage. Check for loose installation of bolts
and nuts. Replace parts as necessary.
Reassembly & Installation
To reassemble, reverse disassembly procedure. To install, reverse removal procedure. Ensure coil spring is well
seated in upper and lower seats. Check rear wheel toe-in. See SPECIFICATIONS & PROCEDURES article in
the WHEEL ALIGNMENT section.
LOWER ARM
Removal
Raise and support vehicle. Remove wheel assembly. Remove stabilizer bar control link nut and bolt. See Fig.
1 . Remove lower strut bolt. Remove lower arm-to-crossmember bolts. Remove lower arm-to-knuckle bolts.
Remove lower arm. Inspect arm for dama
ge, cracks and deformation. Check for damaged or worn bushings.

1991 Mazda MX-5 Miata
SUSPENSION - REAR 1991 SUSPENSION Rear
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MAZDA
1.6L & 1.8L 4-Cylinder - 1986-95
MANUFACTURER'S SUGGESTED SCHEDULED MAINTENANCE
For 1992 and earlier model years, the manufacturer recommends the belt be replaced every 60,000 miles. For
1993-95 model years, the manufacturer recommends the belt be replaced at 60,000 mile intervals for vehicles
sold outside of California. For vehicles sold in California, inspect timing belt at 60,000 and 90,000 miles, and
replace timing belt at 105,000 miles.
REMOVAL & INSTALLATION
TIMING BELT
Removal (MX-3, Protege & 323)
1. Disconnect negative battery cable. Raise and support vehicle. Remove right front wheel. Remove right
splash panels.
2. Remove drive belts and water pump pulley. See Fig. 1
, Fig. 2 or Fig. 3 . Align crankshaft pulley timing
mark with cylinder No. 1 at TDC of compression stroke. Hold crankshaft stationary, and remove
crankshaft pulley bolts and pulley. Remove crankshaft pulley hub bolt and hub.
3. Remove timing belt covers. If timing belt is to be reused, mark timing belt rotation direction. Align
timing marks on camshaft sprocket(s). See Fig. 4
(SOHC) or Fig. 5 (DOHC) . Loosen timing belt
tensioner lock bolt. Temporarily secure tensioner away from belt with spring fully expanded. Remove
timin
g belt.

1991 Mazda MX-5 Miata
MAZDA 1.6L & 1.8L 4-Cylinder - 1986-95

1991 Mazda MX-5 Miata
MAZDA 1.6L & 1.8L 4-Cylinder - 1986-95
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