Auto Climate Control Diagnostics:
 
The auto climate control has an on-board self diagnostic to solve control problems. One of the more complex subsystems in the Z32 is the climate control. The on-board diagnostics actually allows full readout of it's data and adjustments to how it functions besides just returning error codes. This is worked out from the '95 manual. '90 Climate Control is slightly different.

To enter a diagnostic mode:

1. With the ignition switch turned ON, Press AUTO and OFF simultaneously for 5 seconds (step 2 in 1.). This will activate the Monitor Diagnosis Mode (step 3 in 1.)

2. Pressing AUTO again will switch to the Actuator Test Mode (step 4 in 1.).

3. Pressing AUTO again will switch to the Upper and Lower Temperature Difference Adjustment Mode (step 5 in 1.).

4. Pressing AUTO again will switch to a readout of  Trouble Codes (step 6 in 1.).

5. Pressing AUTO again loops back to Monitor Diagnosis Mode (step 3 in 1.).

1.

Monitor Diagnosis Mode:

The control unit will display temperature data in this mode. The step monitor will have the right single dash lit (step 3 in 1.). Temperature data is returned in the display's 'Set' digits.

Use the Mode switch and the Fan switch to toggle through the menu items.
 
Def icon only Ambient temperature ºC(ºF)
Upper vent icon only Upper cabin temperature ºC(ºF)
Lower vent icon only Lower cabin temperature ºC(ºF)
0 Fan & Def icon DEFROST outlet air temperature ºC(ºF)
0 Fan & Upper vent icon VENT outlet air temperature ºC(ºF)
0 Fan & Lower vent icon FOOT outlet air temperature ºC(ºF)
1/4 Fan & Def icon Sunload *1
1/4 Fan & Upper vent icon water temperature *3 ºC(ºF)
1/4 Fan & Lower vent icon Mode door voltage *4 *2
1/2 Fan & Def icon N/A
1/2 Fan & Upper vent icon N/A
1/2 Fan & Lower vent icon N/A
3/4 Fan & Def icon N/A
3/4 Fan & Upper vent icon N/A
3/4 Fan & Lower vent icon N/A
Full fan & Upper vent icon Difference in upper & lower temperatures ºC(ºF)
Full fan & Lower vent icon N/A

*1: One tenth of the value in kcal/h*m² unit
*2: Ten times the value in V
*3: When coolant temp. is below 40ºC(104ºF), indicates 20ºC (68ºF). When coolant temp. is above 40ºC(104ºF), indicates 80ºC (176ºF)
*4 Mode door voltage: 0 = VENT, 5 = DEFROST

Actuator Test Mode:

The climate controller will force actuators to work in this mode. The step monitor should be the right two dashes lit (step 4 in 1.). The 'Set' digits in the display are the Mode door voltage, 0 = VENT, 5 = DEFROST. I'm not really sure what mine means with a 49 listed.  Mode and fan speed can be set independently. When the upper and lower vent icon appears, a stabilized outlet temperature 30ºC(86ºF) is reached after the air mix door has be working for about a minute.

Use the Mode switch to toggle through the menu items.
 
Display


Actuator

Defrost icon Defrost and lower vent icon Upper and lower vent icon Upper vent icon
Mode door DEF DEF/Lower B/L VENT
Intake door FRE FRE 50% FRE REC
Air mix door Full hot Full hot 30ºC(86ºF) Full cold
Compressor OFF OFF ON ON
operating condition of the actuators cannot be checked by indicators alone.

Use the Fan switch to toggle through the menu items.
 
Display


Blower Motor

1/4 Fan 1/2 Fan 3/4 Fan Full fan
Voltage 4V 6V 9V 12V

Upper and Lower Temperature Difference Mode:

Adjustments can be made to the difference in upper and lower target temperatures in this mode. The step monitor should be 3 dashes (step 5 in 1.). The 'Set' digits in the display will show how much of a difference by 'data' numbers in relation to temperature difference.

Using the Fan and Mode switches to raise or lower the data number:
 
 
ºC spec. Data -20 to -1 0 1 to 20
ºC spec. Difference between upper and lower target temperatures -2.0ºC to -0.1ºC 0 0.1ºC to 2.0ºC
ºF spec. Data -36 to -2 0 2 to 36
ºF spec. Difference between upper and lower target temperatures -3.6ºF to -0.2ºF 0 0.2ºF to 3.6ºF
The programmed differences are stored until changed again, or the battery is disconnected.

Trouble Codes:

The auto climate control stores error codes for later retrieval. The step monitor should be 2 dashes with a space in-between (step 6 in 1.). The 'Set' digits will show the number of ignition ON/OFF cycles since the problem was last detected. A dash '-' in the step monitor to the far left indicates a short circuit. A '|' hash in the step monitor on the left indicates an open circuit.

Use the Fan and Mode switches to raise or lower the code to change the desired data or status reading returned.
 
Code Sensor Open circuit Short circuit
Defrost icon Ambient sensor Less than -70ºC(94ºF) Greater than 141ºC(286ºF)
Upper vent icon Cabin upper sensor Less than -38ºC(-36ºF) Greater than 141ºC(286ºF)
Lower vent icon Cabin lower sensor Less than -38ºC(-36ºF) Greater than 141ºC(286ºF)
0 Fan & Def/lower vent icon*1 DEF duct sensor Less than -38ºC(-36ºF) Greater than 141ºC(286ºF)
0 Fan & Upper vent icon  VENT duct sensor Less than -38ºC(-36ºF) Greater than 141ºC(286ºF)
0 Fan & Upper/lower vent icon*2 Lower duct sensor Less than -38ºC(-36ºF) Greater than 141ºC(286ºF)
1/4 Fan and Def icon Sunload sensor Open circuit can not be detected w/ self diagnostic Greater than 1.784kW (1,534kcal/h, 6,087BTU/h)/m²
[0.1657kW (142.51 kcal/h, 565.5 BTU/h)/sq ft.]
*1 One chart in the service manual shows 0 fan with Def/lower vent icon, while another shows 0 fan with Def icon alone.
*2 One chart in the service manual shows 0 fan with Upper/lower vent icon, while another shows 0 fan with Lower icon alone.

Originally posted: 3-5-00

DamonZ

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