AutoClimate Control Diagnostics:
 

The auto climate control has anon-board self diagnostic to solve control problems. One of the more complexsubsystems in the Z32 is the climate control. The on-board diagnosticsactually allows full readout of it's data and adjustments to how it functionsbesides 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 simultaneouslyfor 5 seconds (step 2 in 1.). This will activate the Monitor DiagnosisMode (step 3 in 1.) 2. Pressing AUTO again will switch to the Actuator Test Mode (step 4in 1.). 3. Pressing AUTO again will switch to the Upper and Lower TemperatureDifference 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 3in 1.).

1.

Monitor Diagnosis Mode:

The control unit will display temperature data in this mode. The stepmonitor will have the right single dash lit (step 3 in 1.). Temperaturedata 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), indicates80ºC (176ºF)
*4 Mode door voltage: 0 = VENT, 5 = DEFROST

Actuator Test Mode:

The climate controller will force actuators to work in this mode. Thestep 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 venticon appears, a stabilized outlet temperature 30ºC(86ºF) is reachedafter 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 targettemperatures in this mode. The step monitor should be 3 dashes (step 5in 1.). The 'Set' digits in the display will show how much of adifference 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 batteryis disconnected.

Trouble Codes:

The auto climate control stores error codes for later retrieval. Thestep 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 theproblem was last detected. A dash '-' in the step monitor to the far leftindicates a short circuit. A '|' hash in the step monitor on the left indicatesan open circuit.

Use the Fan and Mode switches to raise or lower the code to change thedesired 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 venticon, while another shows 0 fan with Lower icon alone.

Originally posted: 3-5-00