Ext. temp doesn't display anymore - flashing display

'95 - Automatic Dual zone climate control (CJ2); about a week ago I started the car up and the external temperature no longer shows and hasn't shown since. Instead, the internal set temperature is the only temperature displayed, and it flashes constantly (signaling a fault). This problem messes up the programmer's ability to deliver the right temperature air, so I can't just ignore it.

I figured it was a failed external temp sensor, so I tested it. I swapped a different external temp sensor in its place, and that didn't fix it. I tested the resistance, and it's testing out good. I tested the voltage on the electrical connector at the external temperature sensor, and it's testing out well at 5 volts. So the external temperature circuit is ok, and the sensor itself is ok. So then what would cause the ext. temperature to not display?

Is it possible that the internal temp sensor or one of the sunlight sensors has gone bad and is causing the external temp to no longer display? Or should I assume its the programmer?

This problem is not intermittent. It happened abruptly, which causes me to rule out wiring issues. Any ideas welcome.

The flashing display is telling you that you have a fault in the system. Without knowing what that fault(s) are, we could only speculate on what the problem is.

Does anyone have any knowledge of whether or not anything else can cause the external temperature to no longer display besides the temp sensor, wiring to the sensor, or programmer? I know the sensor and wiring are fine. So if nothing else would cause this issue, then I can assume it's the programmer.

I am having to do some speculation because I don't have a Tech 1. Sorry.

I had a similar experience with my '95. I installed a new sensor and after several cycles (days) of the HVAC system being turned on and the engine being run the controller finally "learned" the sensor and returned to normal operation. That's been about two years and it hasn't been a problem since. It might also help to disconnect the battery for a while, but turn the system off first.

You are assuming you have an outside temp display issue-- that is only one of ten possible faults that set a code that flashes the display for 2 minutes after every key on. You have a fault code that does not allow the system to go through its normal routine where it displays the outside temp. The flashing display should be your concern, not the fact it doesn't go to outside temp mode. Unfortunately, my Mitchell-on-Demand says you have to read code with a Tech I scan tool- it is not accessible without it, so you will need to see a shop that has a Tech I........also it is not the type of code that lites the SES....

From my experience, the most common code is the a/c low refrigerant code- does the same thing- flashes the display-

Try resetting the code by unhooking battery for ten seconds, then keep a/c off and see what happens.....you may get lucky and that is the code and you can deal with that later......

I unhooked the battery cables for most of the day to reset the fault code. I hooked up a different external temp sensor, and when I turned everything on, everything works!! I'm going to drive it several days and see if the fault code reappears. It's kind of a mystery to me but I'm thankful the code is gone at least for now. I know it's not the A/C. I haven't used that for a long time.

If you have used defrost or blend or simply been in "auto" mode and if it has been above 40 degrees- then you have used your a/c.....remember- most common code set is low refrigerant code...........

All is well! I've tested the A/C compressor, and it's not throwing codes. So it must have been the external temp sensor that threw the code, even though it tested out fine on the ohmmeter. Thanks for the insights.