External Temp Sensor vs A/C - 1999 Buick Park Avenue Ultra

As I was driving to lunch yesterday with my A/C blowing full blast (on auto), the fans suddenly all stopped. I looked down at the external temperature display and it showed -21°F. It then changed back to 71°F (I don't know if this was correct or not) and the fans came back on to full blast. This didn't happen again until that evening, wherein I was driving home and the external temperature was just going up and then resetting to really low, the lowest I saw was -36°F, and any time it got really low, the fans would stop. I even tried switching to manual mode by adjusting the fan to high and the temperature to 60°F, and it would start blowing warm (presumably outside) air once the external temperature is detected as really low.
I had decided that it probably wasn't the external temperature sensor that was acting up, but then saw a post where another user had what looked like an actuator problem to a moderator, and his external temperature display jumped up to 140+°F once prior to this (thread 916072 (http://www.automotiveforums.com/vbulletin/showthread.php?t=916072)).
I am now curious as to whether or not anyone can tell me if the air conditioner would be affected by what the external temperature is detected to be. I have some other issues that lead me to think this is more likely part of a bigger central electrical/computer problem, but even if it's not, it seems to me like it would be related to a computer, as I would have expected the A/C to continue blowing (even if just outside air) in an attempt to continue to cool the cabin, but if the outside air temperature was low by at least 90°F, and the A/C stopped blowing because it thought the internal temperature suddenly dropped as well, I would think that temperature would be detected equally far off and the heater would have kicked on (while it was on auto, as it was most of the time). Unfortunately, I didn't think to watch the coolant temp in the DIC, but will be switching it there for the drive home tonight, but any thoughts would be appreciated.
Also, is Standard Motor Parts part# AX32 the correct part? I have seen it listed as "Air Charge Temperature Sensor," and "Air Intake Temperature Sensor," but I don't know if those are accurate descriptions, nor do I know if there is a separate temperature sensor for the external temperature display.

The coolant temp in the DIC was consistent as this happened.
Additionally, I was able to keep the car a decent temperature by switching to recirc and max fan (no auto). Without recirculation, the hot air coming in when it's below 60°F outside (according to the A/C display) keeps it from getting/staying cool at all (with the fan on manual so it doesn't turn off like it does on auto). Anyway, basically, I want to know if I should bother replacing the sensor. As far as I'm concerned, I don't care what the external temperature display says because this car is a junker to me at this point, but if the sensor would affect the A/C and cause it to behave as described in my original post, then it would probably be worth replacing, and it would be even more so worth replacing if it is likely the sensor and that would also affect the engine (though I didn't seem to notice such a thing, presumably it would just run richer when the temp dropped?). I also need to know if the aforementioned part is what I'm looking for. TIA

The "ambient air sensor" for the A/C system, (Part # AX27) is located in the front grill area and mounted to the hood latch vertical brace. It does have an effect on the operation of the auto climate control and nothing to do with engine performance. The sensor will cost about 15 bucks @ Advanced Auto, so yes, it is worth replacing. Do not confuse this sensor with the "Air Charge Temperature Sensor," (intake air temp) sensor Part # AX32. that is located between the air filter box and throttle body. A Pic & part number of the sensor you want is shown below.

Part # AX27

http://img148.imageshack.us/img148/9487/ax27gg5.jpg

there is a separate controler for the climate control system on my 2000 pa it is located behind the glove box and the outside temp and all operation is ran through it

Your OAT (outside Temperature Sensor) is either bad- or the wire to it is broken, or partially broken-- I have seen both scenarios cause a lack of a/c when the climate control thinks the outside temp is below 40 degf..

While waiting for a replacement ambient air sensor to arrive at Advanced Auto (not an SMP AX27, but whatever their computer recommended), I disconnected mine. This caused the external temperature to stop displaying, and my air conditioning worked fine in the morning (no hot sun and a decent outide temperature. However, in the daytime, with the sun bearing down, it would get miserably hot on auto unless I set the temp to 60°F (mininmum), and then it would eventually get too cold, requiring manual fan adjustment. Once the now sensor arrived, I connected it. It said 50°F for a short while (maybe a minute) and then started bouncing around, but not as bad as the original one was (so far). Mostly it was jumping between 87°F (accurate) and 78°F. I didn't see it get lower than that, but I know it was, because when it does the fan starts spinnig down, then it kicks back on when the temperature comes back up. That said, is it possible (ok, plausible) that I got another bad sensor, and can they be tested? It sounds like it could be the wire as well, and that would not be fun, but wouldn't surprise me, as not too long ago my idler pullies both broke, flinging my belts both everywhere, and one might have gotten it, depeding on where it runs to. How should I (or should I even) go about trying to find a break in the wire? Also, do the symptoms mentioned in this post sound like they could be related to the climate control system, or is everything behaving as expected in the different scenarios?

Wait & see what it does after about 40-50 ignition cycles.

Also, it has to be driven to update the reading-it is programmed that way so as not to react to the back end of a hot bus in city traffic..

Alright, I'll wait a while to see what happens, but it is getting worse. It is now getting below freezing (haven't seen negative °Fs yet). Also, sometimes while the temp is jumping around, the EXT will disappear, and this was happening before the replacement too, but I forgot to mention it. That may mean it is more likely a bad wire or controller. Finally, regarding the comment that it has to be driven to update, while this would make sense, it was always high when I start the car after it has been sitting on a hot summer day (higher than it was when I got out & higher than the outside temperature), it would then come down to an accurate temperature. Perhaps this feature does exist, but only when idling, not when off?

It was still doing it after about 30 ignition cycles. Then one day as I pulled off of the highway onto a side road Friday, it dropped to -39°F and stayed there. Since it stayed there, the heat kicked on. I wasn't about to put up with that since I had some miles to drive Sunday, so I checked Sunday morning and it was still at -39°F. I went to unhook the sensor so I could at least sort of have A/C, and I noticed that the wires were loose (clamp had come off and wind was probably blowing them around). I clamped them back onto the bottom of the vertical brace, routed them behind a piece of plastic that looked like that's what it was before, and pulled them tight. Temperature has been right (as far as I know, climate control hasn't been goofy) for over 200 miles now. I think the wires probably broke once it came loose since they were likely quite brittle being 9.5 years old and all (born April 99). Pulling them back how they have always been (albeit tighter than I prefer to bend/pull a wire coming out of the back of the plug) seems to have worked, though I wouldn't call it fixed so much as functional.