Mazda MX-5 Miata (1997+). Manual - part 78

Fig. 4: Heater System Wiring Diagram 

 

1997 Mazda MX-5 Miata 

HEATER SYSTEM 1997 Heater System

  

A/C-HEATER SYSTEM - MANUAL

1997 Manual A/C-Heater System 

A/C SYSTEM SPECIFICATIONS 

A/C SYSTEM SPECIFICATIONS 

DESCRIPTION 

Blower assembly, mounted under right side of instrument panel, contains blower motor, blower resistor and 
fresh/recirculated air door. Evaporator unit, located left of blower case, contains evaporator, evaporator 
thermoswitch and expansion valve. Heater unit, located left of evaporator case, contains heater core, airflow 
mode door and air-mix (temperature blend) door. 

ELECTRICAL COMPONENT LOCATIONS 

WARNING:

To avoid injury from accidental air bag deployment, read and follow all 
SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG 
SYSTEM procedures in AIR BAG RESTRAINT SYSTEM article in the 
ACCESSORIES/SAFETY EQUIPMENT section.

CAUTION: When battery is disconnected, radio will go into anti-theft protection 

mode. Obtain radio anti-theft protection code from owner prior to 
servicing vehicle.

Application

Specifications

Compressor Type

Nippondenso TV12 Rotary 

Vane

Compressor Belt Deflection 

(1)

 

New

5/16-23/64" (8-9 mm)

Used

23/64-25/64" (9-10 mm)

Compressor Oil Capacity 

(2)

 

4.4-5.7 ozs.

Refrigerant Capacity

21.2 ozs.

System Operating Pressures

High Side

200-227 psi (14.0-16.0 

kg/cm

2

 )

Low Side

22-35 psi (1.5-2.5 

kg/cm

2

 )

(1)

Measure with 22-lb. (10 kg) pressure applied halfway between crankshaft pulley and Power Steering 
(P/S) pulley or idler pulley (without P/S).

(2)

Use ND-Oil 9 refrigerant oil.

 

1997 Mazda MX-5 Miata 

A/C-HEATER SYSTEM - MANUAL 1997 Manual A/C-Heater System

  

 

1997 Mazda MX-5 Miata 

A/C-HEATER SYSTEM - MANUAL 1997 Manual A/C-Heater System

  

ELECTRICAL COMPONENT LOCATIONS

OPERATION 

All air control doors are controlled manually by cable from control panel. Blower resistor determines blower 
speed. With blower switch in high position, blower motor is grounded directly through blower switch. With 
blower switch in all other positions, blower motor is grounded through blower resistor and blower switch. 

A/C compressor clutch circuit is completed when A/C relay is energized and pressure switch is closed. A/C 
relay is energized when Powertrain Control Module (PCM) grounds the solenoid circuit of the relay. The PCM 
energizes A/C relay if evaporator thermoswitch is closed and A/C and blower switches are on. The PCM also 
controls A/C relay operation according to engine load. 

ADJUSTMENTS 

TESTING 

A/C SYSTEM PERFORMANCE 

1. Connect manifold gauge set. Operate engine at 1500 RPM. Operate A/C at maximum cooling, recirculate, 

fan on high, vent mode. Close all doors and windows. Place thermometer at center vent outlet.  

2. Allow A/C to stabilize. Ensure high pressure is 200-227 psi (14.0-16.0 kg/cm

2

 ). Read temperature at 

center vent outlet. Ensure temperature is within 39-43°F (3-6°C)  

A/C COMPRESSOR CLUTCH CIRCUIT 

Component

Location

A/C Relay

Right Front Corner Of Engine Compartment

Condenser Fan

Right Front Corner Of Engine Compartment

Blower Resistor

Bottom Of Blower Case

Evaporator Thermoswitch

On Evaporator Upper Case

Pressure Switch

In High-Pressure Line, Between Receiver-Drier & 

Evaporator

NOTE:

For door control cable adjustments, see ADJUSTMENTS in HEATER SYSTEM 
article.

WARNING:

To avoid injury from accidental air bag deployment, read and follow all 
SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG 
SYSTEM procedures in AIR BAG RESTRAINT SYSTEM article in the 
ACCESSORIES/SAFETY EQUIPMENT section.

NOTE:

For test procedures not covered in this article, see TESTING in HEATER 
SYSTEM article.

 

1997 Mazda MX-5 Miata 

A/C-HEATER SYSTEM - MANUAL 1997 Manual A/C-Heater System

  

1. Check WIPER fuse (20-amp) in passenger compartment fuse block. Check AD FAN (additional fan) fuse 

(20-amp) in engine compartment fuse block. If fuses are okay, go to next step. If either fuse is blown, 
check for shorted wiring harness before replacing fuse.  

2. Operate engine at idle. Turn A/C and blower on. Using voltmeter, backprobe Black/Red wire terminal of 

compressor clutch connector. If battery voltage exists, replace compressor clutch. If battery voltage is not 
present, go to next step.  

3. Ensure engine is running. Ensure A/C and blower are on. Using a voltmeter, backprobe Blue/Yellow wire 

terminal of the A/C relay connector. If battery voltage exists, go to next step. If battery voltage does not 
exist, repair open Blue/Yellow wire between AD FAN fuse and A/C relay.  

4. Backprobe Blue wire terminal of A/C relay connector. If battery voltage exists, go to next step. If battery 

voltage is not present, repair open Blue wire between WIPER fuse and A/C relay.  

5. Backprobe Black/Red wire terminal of A/C relay connector. If battery voltage exists, repair open 

Black/Red wire between A/C relay and compressor clutch. If battery voltage is not present, go to next 
step.  

6. Backprobe Blue/Black wire terminal of A/C relay connector. If voltage is Zero volts, replace A/C relay. If 

voltage is not Zero volts, repair open Blue/Black wire between A/C relay and PCM. If wire is okay, check 
PCM operation.  

CONDENSER (ADDITIONAL) FAN CIRCUIT 

1. Check ENGINE fuse (30-amp) in passenger compartment fuse block. Check AD FAN fuse (20-amp) in 

engine compartment fuse block. If fuses are okay, go to next step. If either fuse is blown, check for 
shorted wiring harness before replacing fuse.  

2. Start engine. Turn A/C and blower switches on. Using voltmeter, backprobe Black/Yellow wire terminal 

of condenser fan motor. If battery voltage exists, go to next step. If battery voltage is not present, go to 
step 4).  

3. Turn ignition switch off. Disconnect condenser fan connector. Using ohmmeter, check continuity 

between Black wire of condenser fan connector and ground. If continuity exists, replace condenser fan. If 
continuity is not present, repair open Black wire between condenser fan and ground.  

4. Turn ignition on. Ensure A/C and blower switches are on. Using voltmeter, backprobe Black/White wire 

terminal of condenser fan relay connector. If battery voltage exists, go to next step. If battery voltage is 
not present, repair open Black/White wire between ENGINE fuse and condenser fan relay.  

5. Backprobe Blue/Yellow wire terminal of condenser fan relay connector. If battery voltage exists, go to 

next step. If battery voltage is not present, repair open Blue/Yellow wire between AD FAN fuse and 
condenser fan relay.  

6. Backprobe Black/Yellow wire terminal of condenser fan relay connector. If battery voltage exists, repair 

open Black/Yellow wire between condenser fan relay and condenser fan. If battery voltage is not present, 
go to next step.  

7. Backprobe Blue/White wire terminal of condenser fan relay connector. If battery voltage exists, repair 

Blue/White wire between condenser fan relay and PCM. If wire is okay, check PCM operation. If battery 
voltage is not present, replace condenser fan relay.  

A/C SWITCH 

 

1997 Mazda MX-5 Miata 

A/C-HEATER SYSTEM - MANUAL 1997 Manual A/C-Heater System