1990 - 1996 Corvette: HVAC Diagnostic Codes

On 1990 to 1996 Corvettes equipped with RPO C68 (electronic climate control), it is possible to read the HVAC system diagnostic codes from the climate control panel on the dashboard.

To enter the diagnostic mode, press the fan up and down arrow buttons at the same time until -00 appears on the digital readout.
One you have entered the diagnostic mode, you can scroll through the various parameters by using the up and down fan buttons.
To view the value for a particular parameter, press the "AUTO" fan button.

Note: If you see a "-" next to a parameter value (example: "-105"), you must add "100" to that value to obtain the correct value for that parameter. Therefore, the correct reading would be 205 for this example.

Parameter	Description	Values
0	System Faults (one of these will be set if your air conditioning controls have an LED flashing)	00=No Faults 01= Temp Door Motor Circuit Fault 02= Temp Door Motor Circuit Fault 03 = Ambient Sensor Open 04 = Ambient Sensor Short 05 = In-Vehicle Temp Sensor Open 06 = In-Vehicle Temp Sensor Short 07 = Solar Load Sensor Open 08 = Solar Load Sensor Short 09 = Low Freon Detected 10 = UART Failure
1	Temp Setting	60F to 90F
2	In-Car Temp Sensor	10 = HOT -130 = 230 = COLD
3	Outside Temp Sensor	10 = HOT -130 = 230 = COLD
4	Sun Load Sensor	Max light Max Dark L98 38 183 LT5 115 -110 = 210
5	Ignition System Voltage	0 = 9 Volts -155 = 255 = 16 V
6	Engine Speed (RPM divided by 25)
7	Vehicle Speed
9	A/C System Mode	00 = OFF 01 = Re-Circulation 02 = A/C 03 = Bi-Level 04 = Heater 06 = Defrost 07 = Vent 10 = Manual Re-Circulation
10	Blower PWM	0 = 0 Volts 128 = 14 Volts
11	Program Number	00 = COLD -155 = 255 = HOT
12	Mix Number	-155 = 255 = COLD 00 = COLD
16	Coolant Temperature In degrees C
17	Solar Correction	114 = Max light 128 = max dark
30	Stored Full Hot Value	0 to 50
31	Temp Door Travel Range	100 to 200
34	Temp Door Position Requested	00=Full HOT -153=253=Full COLD
35	Compressor On Time	0.1 second increments
36	Number Of Times Below Critical Time
37	Software Version Number

1990 - 1996 Corvette: HVAC Diagnostic Codes

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