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Old 08-03-2012, 12:14 PM   #1
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Exterior temp off the chart, a/c not cooling

So I have my first problem with my new-to-me 2003 Boxster S. Drove it home today and found the air con is just blowing air, not cooling (car has auto climate control).

And the outside temp reading was completely out of kilter. It started off at about 37 deg C and went up to 46, where it stabilized. Actual temperature was about 25.

There must be a connection. When I first test drove the car, everything was fine. During the week that has passed between the test drive and today, the seller has had the front bumper off to install an emergency trunk release wire hidden behind the tow eye cap, and he thinks he may have damaged/disconnected/dislocated the external temp sensor located behind the bumper.

Would a dysfunctional outside temp sensor cause an erroneous temp reading and make the climate control act this way?

Thanks in advance
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Old 08-03-2012, 12:37 PM   #2
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I guess it's possible? I'm not sure if the 03s are set up the same way, but on my car the temp sensor is on the right side front grille and it rests in a really crappy little plastic hoop. Occasionally it can fall out, and obviously it won't be doing its job. Maybe, if yours is in the same place, it came out of its retainer and is in contact with the radiator. Auto A/C or not, though, if you set it to Low it should blow cold air. Does the A/C work in manual mode?
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Old 08-03-2012, 03:00 PM   #3
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Quote:
Would a dysfunctional outside temp sensor cause an erroneous temp reading and make the climate control act this way?
shouldn't do.. in cold and miserable UK my AC can really chill the interior down.

a common issue on the box (and 996's) is that leaves and dirt collect in the passenger side intake in the corner of the rad and condensor and keeps moisture and damp in there where it rots the rads and condensors from the outside. when i took my bumper off mine (and our other 986) there was a carrier bag full of debris in each. as part of of routine maintenance i drop the bumper every year and clean it out. also after replacing the rads and condensors i've treated the corners to clear wax.

if the a/c is not holding pressure, that is the first place to look
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Old 08-04-2012, 12:08 AM   #4
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No... it does not blow cold air even if set to Low, I just tested.

Not sure how to test if the compressor is working or not. In auto mode, it seems to regulate fan speed an distribution okay, it just is not cooling. I guess that suggests some problem with the compressor or refrigerant.

Maybe I was wrong about it working last week, it was a cool day.

But why would it think it is 46 degrees Celsius outside?
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Old 08-04-2012, 02:27 AM   #5
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Update: Today, for some inexplicable reason, the exterior temperature reading is showing a correct value. Maybe the reading yesterday was a fluke. Will see if this lasts.


Still no cool air, however, not even on full blast manual. Maybe it is as simple as needing a refrigerant recharge. The car has been sitting unused for quite a while.


Given the placement of the engine, is a local indy car a/c specialist likely to be able to work on it?
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Old 08-04-2012, 02:36 AM   #6
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the AC compressor is driven off the drive belt and has a magnetic clutch which engages the compressor, if there is not enough refrigerant in the system the pressure switch shuts the clutch off so the compressor isn't spinning away with nothing in the system.

if you have the engine running and press the A/C button, you'll hear the idle tone change as the compressor adds load onto the belt, you'll probably even notice a slight rpm drop, but if the compressor is working and engaging, you'll be getting cold air anyway. if not, then for some reason the compressor is being prevented from the clutch being engaged.

you should be able to take the car to any A/C service place and they have a machine which connects onto the system runs a pressure test then recharges the coolant; some auto stores do the pressure check for free and that will tell you if there is a leak. if there is a leak and the system isn't holding pressure , i'd bet a buck that a condensor is leaking, most probably on the passenger side in furthest out corner where debris collects..

if it is holding pressure and it's not coming on then either the compressor or clutch is faulty, the pressure switch is faulty.

replacing the condensor is very easy, i've done both of mine as well as the rads and dropping the front valence off and getting to the rads to inspect / clear out debris takes less than 10 mins start to finish.

as a visual inspection you'll see signs of coolant leak down the condensors.


after doing anywork on the A/C system the closed circuit system will need to be recharged by an A/C service place has the machine it hooks up to to recharge the refrigerant and they do charge for that, so it's worthwhile having a look in the intakes for debris, if you do have a place nearby that does a free pressure / system test, take it there, if the result is all clean and good then get the system recharged and you should be off and away.

oh and as an aside, if you do open the system to replace or repair anything, it's probably worthwhile throwing a new reciever/dryer on, again very easy to replace, if you have no idea whan it was last changed.
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Old 08-04-2012, 02:45 AM   #7
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oh by the way, as for the temp sensor, they are simple devices mounted in a black plastic case on a little ring in the front intake. if the car is parked with the sun shining on it, being black, it will read a high temperature on it, or if parked in warm still air, will read slightly higher until it gets into a free flowing ambient air where the actaul temperature will be measured.




side note:
temperature is not constant is affected by many local factors, the AGW/CC crowd that would have consign our Porsche's to the scrapheap to drive around, like them, in a Toyota Pious, use this very situation by the placement of temp sensors in locations that will read higher temps than actual.. Watts Up With That?: weather_stations Archives
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Last edited by Bruce Wayne; 08-04-2012 at 02:50 AM.
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Old 08-04-2012, 03:28 PM   #8
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Quote:
Originally Posted by politby View Post
Update: Today, for some inexplicable reason, the exterior temperature reading is showing a correct value. Maybe the reading yesterday was a fluke. Will see if this lasts.


Still no cool air, however, not even on full blast manual. Maybe it is as simple as needing a refrigerant recharge. The car has been sitting unused for quite a while.


Given the placement of the engine, is a local indy car a/c specialist likely to be able to work on it?
Find a good Porsche-qualified indy mechanic in your area and let them diagnose it. It shouldn't take very long. Maybe just a loose wire or low refrigerant.
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