Mazda Training manual - part 289

AIR CONDITIONING 
SG02 - Control System [Manual Air Conditioning]

 

 

SG02-7

TC070-15-01H

 
Evaporator temperature sensor 
 
A/C signal on/off is controlled by the climate control unit turning the A/C signal 
(magnetic clutch) on and off based on the temperature of the air passed through the 
evaporator when both the A/C and fan switches are on. This keeps the evaporator 
surface temperature within the specified range to prevent the evaporator from being 
frosted. 
 
Look at the chart below, Control Reference Value. The predetermined value “t1” must 
be above freezing point. The difference between “t1” and “t2” are usually 2 – 3 ºC. 
 

                  

 

 

t1 =4.5, t2=5.5 (Mazda 3) 

 
The difference value in temperature between “t1” and “t2” is referred as hysteresis 
that prevents continuing repetition of changes ON and OFF at a specified 
temperature.   
 

Character of Evaporator Temperature Sensor 

   

 

 
               Temperature – Resistance                    Temperature – Voltage (PCM input) 
 

AIR CONDITIONING 
SG02 - Control System [Manual Air Conditioning]

 

 

SG02-8

TC070-15-01H

 
Look at both graphs, “Temperature – Resistance” and “Temperature – Voltage (PCM 
input)” and read the resistance and voltage at each given temperature as below. 
 
Resistance                       kilo-ohm, Voltage                      V at -10 ºC 
 
Resistance                       kilo-ohm, Voltage                      V at 0 ºC 
 
Resistance                       kilo-ohm, Voltage                      V at 10 ºC 
 
Insert “higher” or “lower” in the blanks of the explanation below. 
  
The higher temperature it senses, the                     resistance it creates, therefore the 
CPU detects                     voltage.  
 
Look at the wiring diagram below. The left one shows the circuit of evaporator 
temperature sensor extracted from the control system wiring diagram. And the right 
one is a rearranged diagram of the circuit. 
 
The evaporator temperature sensor is grounded through the climate control unit. The 
circuit operates with 5 V power supply. The voltage between the resister R and the 
evaporator temperature sensor varies according to the temperature that the sensor 
senses. The CPU detects this variation of the voltage (potential) which is equivalent 
at the terminal N of the climate control unit. 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
What do you think is the voltage at the terminal N if the resistance of the evaporator 
temperature sensor is 0 ohm? 
                                                                                             V 
 
What do you think is the voltage at the terminal N if the resistance of the evaporator 
temperature sensor is infinity? 
                                                                                             V 
 
Apply the ohm’s low and calculate the constant value of the resister R’s resistance.  
 
                                                                                             ohm 
 

AIR CONDITIONING 
SG02 - Control System [Manual Air Conditioning]

 

 

SG02-9

TC070-15-01H

 
A/C relay 
 
A/C relay is classified as Type A as shown in the table below. Its function is to be 
checked by measuring the continuities.  
 
       
                                                                
 
 
 
 
                                                                            * 

 * It requires supplying battery voltage.  

 
Magnetic clutch 
 
 Mazda 3 [Z6, ZY]                                         Mazda 3 [LF, L3] 
 

   

 

 
 
 
 

1. Bolt 
2. Pressure plate 
3. Shim 
4. Snap ring 
5. A/C compressor pulley 
6. Screw 
7. Clamp 
8. Screw 
9. Stator and thermal protector 
10. A/C compressor body 

1. Bolt 
2. Pressure plate 
3. Shim 
4. Snap ring 
5. A/C compressor pulley 
6. Snap ring 
7. Screw 
8. Clamp 
9. Stator and thermal protector 
10. A/C compressor body 

 

 

AIR CONDITIONING 
SG02 - Control System [Manual Air Conditioning]

 

 

SG02-10

TC070-15-01H

 
A bimetallic (Indirect sensing type) type thermal protector is shown in the figure below.  
 

          

 

1. Thermal protector                                                                 

 

                                                                                     Mazda 3 
 
 
 
Magnet clutch function can be checked by directly applying the battery voltage as 
shown in the figure below.