1990 - 1996 Corvette: HVAC Diagnostic Codes
Estimated Reading Time: 1 MinutesOn 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 |
Thanks so much for sending me this, I am sure it will help. I reflushed the heater core and had very good flow, so I am sure its in the contols somewhere. I had to drive about 200 miles this week in 30 degree weather. I finally used duct tape to cover the vents near the windshield wipers and that kept the car a little warmer inside so I think it has something to do with the temp door. Unfortunely now I have another problem with my service engine light coming on and my code reader says it cannot get a connection. The car runs fine but when it gets to operating temprature and I stop at a light it starts idleing rough and the service engine light comes on, then it smooths out. The light is not on when i first start the car only after driving a while.....it just never ends !!!!!! But I do love my Vette. I will let you know how the heater thing goes.........THANKs Again !!