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I have a 2000 e39 touring wagon with 66k. I just had a baby with my wife on May 24th. My son can't be in h extreme hot or cold yet. My air conditioning has only worked twice in the past 3 weeks. I noticed the only 2 times it worked were the only 2 times my outside temperature reading was correct. I obviously have an incorrect temp reading. It has been 80 plus each day, and my temp reading has been in the 20's each day but the 2 days it worked. I just ordered a new outside temp sensor, but if I disconnect mine until the new one comes will the AC work again. Compressor good and system full. Need it in case I have to take my son somewhere. Any one with experience in AC failure due to inoperable outside temp sensor? Any help will be greatly appreciated.
 

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I don't think the outside temp sensor should impact the A/C as much as the inside temp sensor but I don't know the algorithm BMW uses for its climate control.

Plenty of people have damaged/lost outside temp sensor and I don't any of them ever reported A/C problems inside the car. I suspect that you might have either A/C problems (coolant levels good) or perhaps your final stage resistor might be bad? Do a search on "FSR" or "final stage resistor" and see what you think.

However, all that said, replacing the outside air temperature probe is simple and cheap but check out threads on the FSR as well....
 

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I have just done some previous post reading and it seems as though a malfunctioning one will cause the AC to not operate. But when one breaks off, or quits completely it goes to a fail safe mode and reads -40 degrees. The computer then knows its incorrect and it allows AC to work. All levels and other connections on the car are correct. I will try what you recommended searching though. This is very frustrating when it is 90 degrees and humid every day lately. Thank you
 

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Good find on the info, Russell! In that case, I suggest you simply remove the temperature sensor and let the car read an open circuit and thus fall into the -40 failsafe mode. In the meantime, order a new one and see if that fixes the problem.
 

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In fender well or under bumper cover.

I can't find this stupid thing. Is it better to go in through the fender well or under the bumper cover? I am having some time finding it.
 

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It may be missing if you've hit a curb recently.

You can see it (assuming it is there) by looking between the bumper and the splash guard in front of the passenger front wheel. It is a short rod type gizmo. No need for jacks & no need to remove anything.

sorry for the multiple edits... I was just trying to describe it better
 

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You can see it (assuming it is there) by looking between the bumper and the splash guard in front of the passenger front wheel. It is a short rod type gizmo. No need for jacks & no need to remove anything.
This reminded me of the replacement problem I had three months ago when I replaced my ambient temperature sensor.

It was easy to buy a new $30 ambient temperature sensor from Pacific BMW (see photo below of mine); and it was easy to plug the new sensor into the wires hanging down from my E39 ... but I still don't know where the bracket is that attaches it to the underside of the car. I ended up wrapping it around the wires shown in the photo below and it has worked fine ever since.

Since the question of exact location is unrelated directly to this thread, I just posted a separate thread asking for a photo or diagram of the attachment point to the underside of the BMW ( http://www.bimmerfest.com/forums/showthread.php?t=101296).

Back to the topic on this thread ... in my case, I didn't realize the AC was NOT working properly at the -40 indicated temperature on the dash display due to the missing temperature sensor. It was blowing cool but not cold air for about a month from the time I bought the bimmer to when Pacific shipped me the backordered ambient temperature sensor. I erroneously concluded the A/C was working but it was just cool outside (see corrections in thread http://www.bimmerfest.com/forums/showthread.php?t=90159 ).

When I plugged in the sensor, the AC took about two hours to start working. Interestingly, the temperature slowly climbed, at about a degree or so a minute, from -2 degrees indicated to the 45 or so degrees actual (I snapped moving photos of the temperature climb as I was test driving the bimmer - these are posted in BMW general thread 286 http://www.bimmerfest.com/forums/showthread.php?t=286).

From then on, I had trouble working the AC properly, until I accidentally ran into an excellent bimmerfester AC control setup thread http://www.bimmerfest.com/forums/showthread.php?t=98444&page=1

So, in my experience:
o The bimmer ran fine without the ambient temperature sensor
o But the air conditioning system failed to work properly
o With the ambient temperature sensor plugged into the wires, the AC worked fine
o But not until the first few hours "settling time" occurred
o And not until I learned the set-up-and-forget settings for the E39 AC

Now, and for the past month or so, the A/C has been working just fine.

If I only had a photo or diagram of the bracket which holds the ambient temperature sensor and harness connector to the bimmer ... :)
 

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If I only had a photo or diagram of the bracket which holds the ambient temperature sensor and harness connector to the bimmer ...
Long after that job was completed, I was made aware of THIS most excellent of articles detailing every step of a BMW E39 outside temperature sensor and bracket repair procedure, including the splicing of the wires necessary when the original sensor is pulled off by a curb or other roadside hazard.
http://www.alisons.us/bmw/tempsensor

 
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