I have 1990 with automatic temp control. More often then not the outside temp reading will drop until it reads -10*. The car will then stop cooling in the summer. If I set the temp to 60* the car cools fine.
I cant remember the exact trouble code but it is along the line of a ground problem. From what I can gather from the FSM the controler does all the ground work.,I have replaced the outside temp sensor with no luck. has anyone experanced anything like this.....

 

Disconnect the negative battery cable for a couple of seconds then reconnect it.

Turn the ignition On and the C68 system will recalibrate itself. After about 30 seconds you should hear the blower motor turn on indicating the calibration is done. You can manually turn the fan off.

If the correct outside temp. is not displayed in the LCD you still have a problem.

 

Yep tried that, no luck.

 

Go back to the FSM, locate the Electronic Automatic Air Conditioning section then troubleshoot the fault code using the diagnostic tree. Could be something as simple as a pinched wire, but following the manual will make finding it much easier since it provides wire colors, connector locations and pin numbers to check, good luck.

 

FSM really doesnt address the issue.That was the first thing I did. I was suprised it didnt offer more help. Ill look again and see if I missed something......

 

Sensor is used along with the Sun Load or Inside Temp Sensor to calculate Temp Door Position and Blower Speed - except at 60 or 90 which overrides these signals and gives you Max Cool or Heat. Sensor is simply a thermistor meaning that as it heats up, it loses resistance so more of the reference signal reaches ground. That voltage drop is used by the Processor to calculate the Outside Air Temp and with yours dropping to -10 degrees, the circuit is opening. Since you bought a new Sensor, that's either in the wire or the Programmer (which is the Processor) may have a weak solder joint. Start by grounding the sensor lead - that should display whatever MAX is burned into the Processor. I'd then ohm out the wire between the Sensor and Programmer or at least wriggle it around at the Sensor. Examine the connector closely - you may want to take apart the Weatherpak to make sure the Connector is securely crimped to the wire. Check Programmer Ground, though if it was losing that, everything would go blank. Aim a hair dryer at the Programmer when the sensor is working - particularly if it works cold - and if it duplicates the problem, it's probably a bad solder joint on the Board. After troubleshooting or replacing parts, disconnect and reconnect the battery to reset the Programmer - otherwise, nothing may work.