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2008 - MX-5 - HVAC

CLIMATE CONTROL UNIT INSPECTION

1. Turn the ignition switch to the ON position.
2. Connect the negative (-) lead of the tester to body ground.
3. By inserting the positive (+) lead of the tester into each climate control unit terminal, measure the voltage according to the terminal voltage table.

Terminal Voltage Table (Reference)



Terminal

Signal name

Connected to

Measurement condition

Voltage (V)

Inspection item (s)

A

IG2

A/C 7.5 A fuse

IG SW ON

B+

  • Wiring harness: continuity, short circuit (Climate control unit— fuse: A—A/C 7.5 A)

  • A/C 7.5 A fuse

IG SW LOCK

1.0 or less

  • Wiring harness: continuity, short circuit (Climate control unit— fuse: A—A/C 7.5 A)

B

B+

ROOM 15 A fuse

Under any condition

B+

  • Wiring harness: continuity, short circuit (Climate control unit— fuse: B—ROOM 15 A)

  • ROOM 15 A fuse

C

Blower fan speed control

Power MOS FET

Fan stopped

1.0 or less

  • Wiring harness: continuity, short circuit (Climate control unit—power MOS FET: C—C)

  • Power MOS FET

Fan: manual 1 (LO) — 24

2.7—3.4

Fan: manual 25 (HI)

9.6

D

TNS signal

TNS relay

Headlight switch OFF

1.0 or less

  • Wiring harness: short circuit (Climate control unit—TNS relay: D—D)

  • TNS relay

  • Headlight switch

Headlight switch ON

B+

  • Wiring harness: continuity, short circuit (Climate control unit—TNS relay: D—D)

  • TNS relay

  • Headlight switch

E

Blower motor feedback

Power MOS FET

Fan stopped

B+

  1. Wiring harness: continuity, short circuit (Climate control unit—power MOS FET: E—B)

  2. Power MOS FET

  3. Blower motor

  4. Blower relay

  5. HEATER 40 A fuse

  6. Power MOS FET replacement

Fan: manual LO

8.17

Fan: manual HI

0.6

F

Panel control signal

Instrument cluster

Headlight switch OFF

0

  • Wiring harness: continuity (Climate control unit—instrument cluster: F—1F)

  • Instrument cluster

  • Climate control unit: terminal voltage (D)

Headlight switch ON

2.7

  • Wiring harness: short circuit (Climate control unit—instrument cluster: F—1F)

G

Actuator power

  • Air intake actuator

  • Air mix actuator

  • Airflow mode actuator

IG SW ON

B+

  • Wiring harness: continuity, short circuit (Climate control unit— air intake actuator, air mix actuator, air flow mode actuator: G—A, A, A)

  • Air intake actuator

  • Air mix actuator

  • Airflow mode actuator

IG SW LOCK

1.0 or less

H

GND

Body ground

Under any condition

1.0 or less

  • Wiring harness: continuity (Climate control unit—GND: H—GND)

I

Plus Signal

J

K

A/C

Refrigerant pressure switch

A/C switch ON, fan switch at 1st

1.0 or less

  • Wiring harness: short circuit (Climate control unit—refrigerant pressure switch: K—A)

A/C switch OFF

B+

  • Wiring harness: continuity, short circuit (Climate control unit—refrigerant pressure switch: K—A) (Refrigerant pressure switch—PCM: C—1J)

  • Refrigerant pressure switch

  • PCM: terminal voltage (1J)

L

M

Evaporator temperature sensor input

Evaporator temperature sensor

Compared with temperature detected by evaporator temperature sensor

Refer to graph 1

  • Wiring harness: continuity (Climate control unit—evaporator temperature sensor: M—B, S—A)

  • Wiring harness: short circuit (Climate control unit—evaporator temperature sensor: M—B)

  • Evaporator temperature sensor

N

Rear window defroster operation

Rear window defroster relay

Rear window defroster switch OFF

B+

  • Wiring harness: continuity, short circuit (Climate control unit—rear window defroster relay: N—E)

  • Rear window defroster relay

Rear window defroster switch ON

1.0 or less

O

P

Q

R

S

Sensor GND

Evaporator temperature sensor

Under any condition

1.0 or less

  • Wiring harness: continuity (Climate control unit—GND: S—GND)

T







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