1991 MAZDA MIATA heater

ELECTRICAL COMPONENT LOCATOR
1991 MAZDA ELECTRICAL COMPONENTS
BUZZERS, RELAYS & TIMERS
BUZZERS, RELAYS & TIMERS LOCATION
CIRCUIT PROTECTION DEVICES
CIRCUIT PROTECTION DEVICES LOCATION
CONTROL UNITS
ComponentLocation
ABS System
Check Valve RelayOn top of ABS pump motor.
Motor RelayOn top of ABS pump motor.
Buzzer & Timer UnitOn bracket, behind left side of dash.
See Fig. 1
.
Circuit Opening RelayOn bracket, behind left side of dash.
See Fig. 1
.
Cooling Fan RelayIn engine compartment fuse/relay
block. See Fig. 1
.
Dashboard Illumination Lights RelayOn bracket, near master cylinder. See
Fig. 1
.
EFI Main RelayIn engine compartment fuse/relay
block. See Fig. 1
& Fig. 2 .
Fuel Pump RelayBehind left front kick panel.
Headlight RelayOn bracket, near master cylinder. See
Fig. 1
.
Headlight Retractor RelayOn bracket, near master cylinder. See
Fig. 1
.
Horn RelayOn bracket, behind left side of dash.
See Fig. 1
.
Ignition RelayIn engine compartment fuse/relay
block.
Turn Signal/Hazard Flasher RelayOn bracket, behind left side of dash.
See Fig. 1
.
ComponentLocation
Fuse BlockBehind left side of dash.
Fuse/Relay BlockIn right rear corner of engine compartment, near firewall.
See Fig. 2
.
Heater Blower Motor Circuit BreakerIn passenger compartment fuse block.

1991 Mazda MX-5 Miata
ELECTRICAL COMPONENT LOCATOR 1991 MAZDA ELECTRICAL COMPONENTS

1991 Mazda MX-5 Miata
ELECTRICAL COMPONENT LOCATOR 1991 MAZDA ELECTRICAL COMPONENTS
Microsoft
Sunday, July 05, 2009 2:15:23 PMPage 1 © 2005 Mitchell Repair Information Company, LLC.
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CONTROL UNITS LOCATION
SENDING UNITS & SENSORS
SENDING UNITS & SENSORS LOCATION
MOTORS
MOTORS LOCATION
SOLENOIDS & SOLENOID VALVES
SOLENOIDS & SOLENOID VALVES LOCATION
ComponentLocation
ABS Control UnitBehind center of dash, near ECU.
Cruise Control UnitBehind left side of dash, above fuse block.
Engine Control Unit (ECU)Behind center of dash. See Fig. 2 .
Supplemental Safety Restraint (SRS)
ModuleBehind left side of dash. See Fig. 3 .
ComponentLocation
ABS Wheel SensorsOn each front & rear wheel hub
assembly.
Airflow MeterConnected to air filter housing. See Fig.
2 .
Atmospheric Pressure SensorBuilt-in ECU.
Brake Fluid Level SensorInside brake master cylinder.
Coolant Temperature SensorOn water outlet, at left rear of engine. See
Fig. 2
.
Cooling Fan ThermoswitchOn thermostat housing.
Crank Angle SensorOn right rear side of cylinder head. See
Fig. 2
.
Intake Air ThermosensorIn airflow sensor unit.
Oil Pressure SensorOn left side of engine near oil filter.
SRS Crash/Impact Sensors
FrontOn center, left and right front of
vehicle. See Fig. 3
.
CenterBehind center of dash. See Fig. 3 .
Throttle Position Sensor (TPS)Mounted on side of throttle body. See
Fig. 2
.
ComponentLocation
A/C-Heater Blower MotorBehind left side of dash.
Wiper MotorOn right side of firewall.

1991 Mazda MX-5 Miata
ELECTRICAL COMPONENT LOCATOR 1991 MAZDA ELECTRICAL COMPONENTS
Microsoft
Sunday, July 05, 2009 2:15:23 PMPage 2 © 2005 Mitchell Repair Information Company, LLC.

Fig. 3: Interior Fuse Panel Identification
Courtesy of MAZDA MOTOR OF AMERICA, INC.
Fuse & Circuit Breaker Identification
11 - 15 Amp (Blue) Engine Cooling Fan
12 - 10 Amp (Red) Gauges, Warning Lights, Turn Signal Lights, Cruise Control
13 - 15 Amp (Blue) Air Bag
14 - 30 Amp Heater
15 - Empty
16 - 30 Amp (Green) Power Windows
17 - 20 Amp (Yellow) Wipers, Washers
18 - Empty
19 - 15 Amp (Blue) Taillights
20 - Empty
21 - 15 Amp (Blue) Shift Lock, Cruise Control, Horn, Stoplights
22 - 15 Amp (Blue) Hazard Warning Lights

1991 Mazda MX-5 Miata
FUSES & CIRCUIT BREAKERS Fuses & Circuit Breakers 1990-95 Mazda
Microsoft
Sunday, July 05, 2009 2:15:54 PMPage 4 © 2005 Mitchell Repair Information Company, LLC.

HEATER SYSTEM
1990-92 Heater Systems
DESCRIPTION & OPERATION
Heater case, mounted under center of instrument panel, contains airflow mode door and air-mix (temperature
blend) door. See Fig. 1
. Blower case, mounted under right end of instrument panel, contains recirculated/fresh
air door. All doors are controlled manually from control panel by cable.
Blower motor relay, in left rear corner of engine compartment (on relay cluster), supplies power to blower
motor. Blower resistors, on bottom of blower case, determine blower speed.
Fig. 1: Exploded View of Heater Case

Courtesy of MAZDA MOTORS CORP. 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
HEATER SYSTEM 1990-92 Heater Systems

1991 Mazda MX-5 Miata
HEATER SYSTEM 1990-92 Heater Systems
Microsoft
Sunday, July 05, 2009 2:12:14 PMPage 1 © 2005 Mitchell Repair Information Company, LLC.
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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
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.
3. If battery voltage is present, turn off blower switch and A/C switch (if equipped). Check voltage at
Blue/Red wire terminal of blower resistor 1-wire connector. If no voltage is present, replace blower
motor. If battery voltage is present, check voltage at Blue/White wire terminal of blower resistor
connector.
4. If no volta
ge is present, replace blower resistor. If battery voltage is present, check voltage at Blue/Red 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.
NOTE: Blower resistor uses a 1-wire connector and a 4-wire connector. The wire
in the 1-wire connector is Blue/Red, and one of the wires in the 4-wire
connector is Blue/Red. Check voltage at appropriate wire.

1991 Mazda MX-5 Miata
HEATER SYSTEM 1990-92 Heater Systems
Microsoft
Sunday, July 05, 2009 2:12:14 PMPage 2 © 2005 Mitchell Repair Information Company, LLC.

wire terminal of blower resistor 4-wire connector. If no voltage is present, replace blower resistor.
5. If battery voltage is present, check voltage at Blue/Green wire terminal of blower resistor connector. If no
voltage is present, replace blower resistor. If battery voltage is present, check voltage at Blue/Yellow wire
terminal of blower resistor connector.
6. If no voltage is present, replace blower resistor. If battery voltage is present, turn ignition on and blower
switch to 4th position (high). Check voltage at Black wire terminal of blower switch connector. If battery
voltage is present, repair wiring between blower switch and ground.
7. If no voltage is present, turn ignition switch, blower switch and A/C switch off. Check voltage at
Blue/White wire terminal of blower switch connector. If no voltage is present, repair wiring between
blower resistor and blower switch.
8. If battery voltage is present, check voltage at Blue/Red wire terminal of blower switch connector. If no
voltage is present, repair wiring between blower resistor and blower switch. If battery voltage is present,
check voltage at Blue/Green wire terminal of blower switch connector.
9. If no voltage is present, repair wiring between blower resistor and blower switch. If battery voltage is
present, check voltage at Blue/Yellow wire terminal of blower switch connector. If battery voltage is
present, replace blower switch. If no voltage is present, repair wiring between blower resistor and blower
switch.
BLOWER MOTOR
Disconnect 2-wire connector from bottom of blower motor case. Apply battery voltage across terminals.
Replace blower motor if it does not operate.
BLOWER SWITCH
With blower switch in positions indicated, check continuity between specified terminals of blower switch
connector. See Fig. 2
. If continuity is not as specified, replace blower switch.

1991 Mazda MX-5 Miata
HEATER SYSTEM 1990-92 Heater Systems
Microsoft
Sunday, July 05, 2009 2:12:14 PMPage 3 © 2005 Mitchell Repair Information Company, LLC.

Fig. 2: Testing Blower Switch
Courtesy of MAZDA MOTORS CORP.
REMOVAL & INSTALLATION
CONTROL PANEL
Removal & Installation
Remove rear center console assembly. Remove vent outlets from center panel assembly. Remove center panel
assembly. Remove control panel screws. Pull control panel from center panel and disconnect cables. To install,
reverse removal procedure.
HEATER CORE
Removal & Installation
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
HEATER SYSTEM 1990-92 Heater Systems
Microsoft
Sunday, July 05, 2009 2:12:14 PMPage 4 © 2005 Mitchell Repair Information Company, LLC.

Drain coolant. Disconnect heater hoses at engine compartment firewall. Remove grommets from holes (if
equipped). Remove instrument panel. Remove heater case. Disassemble case and remove heater core. See Fig.
1 . To install, reverse removal procedure. Fill cooling system.
INSTRUMENT PANEL
Removal & Installation
Obtain code number and deactivate audio anti-theft system. Disconnect negative battery cable. Remove all
components in order listed in illustration. See Fig. 3
. To install, reverse removal procedure.
Fig. 3: Exploded View of Instrument Panel

Courtesy of MAZDA MOTORS CORP.
WIRING DIAGRAM

1991 Mazda MX-5 Miata
HEATER SYSTEM 1990-92 Heater Systems
Microsoft
Sunday, July 05, 2009 2:12:14 PMPage 5 © 2005 Mitchell Repair Information Company, LLC.