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Hi all,
I have a 2000 9-3 Aero. Under normal conditions my air-con works well, however recently during extreme heat it dies after about 45 mins and only leaves me with a fan. This occurs after the first 'start up for the day'. The cabin sensor was screaming - so I did remove and clean it / vacuum dust etc - and I reset the ACC. No bars appeared during the reset - only 0.
When I say extreme - it was approx 45 degrees C (113 F) the other day.
The cabin sensor is still screaming - but only just a little. The cigarette lighter was in place - but not used during that period.
Is this just a case of refrigerant re-gas needed - or should I get a new cabin sensor - or both?
Engine Wise - the car was fine, and I had no over-heating.
Is there anything else I should check?
 

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Cabin temp sensor - I've renovated loads of these and when cleaned thoroughly they are absolutely quiet. If yours still makes a noise and you've sucked the dust out I suggest the issue is the end bearings.. The bottom of the sensor can be unclipped to allow a drop of oil to be put on the end of the spindle and its also possible to get a drop on the top end.

However I don't think thats your issue as long as the inevitable ball of dust was removed from the thermocouple.

When you say the air con gives up after 45 minutes, does it work again later? I had this issue with a Honda Civic and solved it by taking the clutch plate off the compressor pulley and removing a shim. Not 100% sure how it happens but apparently the faces of the magnetic clutch corrode and the gap slightly increases. Increased heat apparently expands the gap a bit more, and at a natural "off" cycle of the compressor it then can't re-clutch itself because the gap's too big. Thats my simplistic understanding anyway.

There was a 0.5 mm shim in there, and its run without issue ever since (a few years).

If you Saab air con is cold on the occasions when it is working, it might not need a re-gas. If it did, surely the air wouldn't be cold??

You reset the ACC - on the 9-3, there is a fault code for failure of the cabin temp sensor and cabin fan voltage, but not for low gas, or the failure of the cabin fan speed controller, a frequent fail on 9-3s. In my experience (two failures) and knowledge, they don't go intermittent though. They fail to a fixed fan speed, usually zero or max. So it doesn't sound as if yours has failed.

Based on your description, and the assumption that the system's low and high pressure switches are not being tripped, I'd try the shim removal based on my Honda experience.

For future readers - all the above relates to the ACC version. Basic AC version is completely different.
 

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I assume that you don't get any cool air even if you set the temp to LO (which will force full operation).

Ideally, you have WIS and access to a Tech II to tell what's going on.

The compressor itself has an overheat cutout. You might want to check how hot it's gotten. Given the rest of your environment, even being a little low on refrigerant could cause your compressor to overheat.


More generally,
 

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I would check refrigerated pressures first - it does sound like a safety cutout happening... whether pressure or heat. If not that, then EdT's temp sensor would be my next stop.

I did run into Doug's scenario once on a Saab, but found no shim was top little and the one there was too much, and there was nothing in the middle so the only recourse was to change the clutch. I would never do that again... the small cost savings vs changing the whole compressor just isn't worth it.
 

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Mort: Ed and Jvan have this sussed. I'd get a set of gauges. A reasonable set can be had for $50 usd. This site will help you understand what you are seeing: R134a Pressure Gauge Readings .

Learn how to hook them up to test in your driveway. See where you stand when it's working. Carry them with you on the road. Next time it acts up, throw them on there (you can do it in dress clothes, it's easy) and see what comes up.

You might also learn to analyze whether the clutch is engaging or not. If it's not engaging when hot, that's another clue. It might not be the issue since another fault will cause the ACC to not send voltage to engage the compressor under certain conditions. But it's information you can use. It will be harder to figure out without getting a little dirty.

Just as a rough check, I'd also pull the belt. See if the A/C bearing is loose or rough. If so, that's another indicator that you need a clutch done and/or a compressor change.

Jvan: Changing just the clutch or bearing makes sense is everything is working well and you don't have the facilities to do your own discharge/recharge. Usually it's just the clutch or bearing that goes out on these (not so sure that's Mort's issue). But, it's a royal PITA job because you can't get in there except through the wheel well/inner fender for most of the work. It's like looking through a keyhole to see how a room is decorated. It can also be a double PITA when the pulley unit doesn't want to come off, or go back on. I might lean your way next time... even if I have to pay someone for the charge process.
 

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Recharging the system is easy - you need a vacuum pump and manifold gauge set, but these days that's $125 or so, not too bad. It's emptying the system that's annoying since you cant afford a recovery tank yourself and someone is going to charge you to do it for you. I suppose if you're lucky the system is already empty, as ones I've encountered usually are.

A whole AC rebuild- compressor, valve, dryer - isn't huge cash, and the difference between a 120,000 mile old system and a fresh system is everything! That two years zero problems car stays icy cold even in 110F weather.

Filling by pressure isn't perfect, they expect you to do it by weight these days, but pressure got us by for decades and as long as you're cautious it's reasonably reliably IME. Just monitor your fill, your pressure, and your vent temps.

One thing I will advise - California now requires self sealing refrigerant cans... they cost a little more but mean you don't waste R134 and that's awesome. The 9-3 uses something like 30oz of refrigerant so it's 2.5 cans... something like that anyway... you always have half a can left. Self sealing can means you have one ready to go next time. :)
 

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Yeah, it's the vac pump I lack. I have a mickey-mouse one that works off an air compressor. Simple device, but your compressor has to be able to run flat out for a half hour. I still have the tool but no compressor now, so I'd need something new.

When we charged my 'vert at my mechanic buddy's garage, he used his fancy machine to do it... pretty much just hooked it up, set the dials and away it went. A little while later I was charged and ready to go. What a breeze. (EDIT: no pun intended).
 

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Yeah, those modern machines are ace... and coming down quite a bit in price (from over $5k to under $3k) but well out of range of someone who won't be doing AC work every day.

I have read that the air driven pumps can't hit full vacuum... something about fluid dynamics or somesuch. Electric Chineseum ones are in the $50-$70 range and while probably annoyingly slow for a pro, are just fine for DIY. You don't need to save the extra eight minutes you win with a 8cfm model over a 3-4cfm model. A whole kit with pump and gauges is under $150, so on the second recharge you're making money! :)
 

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Not bad. I don't know prices across the country, but in MA a vac/recharge was $150. So, that's a one time payback. I already have gauges, so it's in my interest to invest in the pump.
 

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I don't know about Australia, but in Canada R-134a is to be used only by licenced technicians. There is no shelf of fix-it-yourself cans at the local parts store, and I nearly got sent back to Detroit from Windsor once, because I did not realize this. So getting the system recharged by weight by a shop that has the proper equipment is the only good choice.

A quick check with a dollop of water might be enough to tell if the compressor is overheating: splash the water on, if it sizzles and vaporizes, the compressor is probably too hot. An infrared thermometer would be easier but less fun.
 

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I dunno about Canada or Australia, but in the US getting your EPA refrigerant license isn't difficult or expensive. I'm licensed for automobile AC repair!
 

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An infrared thermometer would be easier but less fun.
I bought an infrared thermometer from HF a while back. Pick them up for $20 or less when on sale: 12:1 Infrared Laser Thermometer . Easy, accurate, simple.

As one reviewer noted: "I now know the temperature of everything".

I got it mostly because I moved to a hot climate and it's just a barrel of fun and amusement... but you'd be surprised how many practical uses it has. I use it in the garage, in the kitchen, and lots of other places. The most innovative is a friend of mine who uses it on his big excavators and large trucks to pinpoint which track or wheel bearing has gone bad. You can check brake rotors temps, etc. Definitely a good investment.
 
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