 |
|
|
1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Air conditioning systems are extremely picky about many factors outside of the refrigerant. Generally, SAAB 900 air conditioners work pretty good with R134. They are expansion valve systems which will adjust themselves automatically for the proper pressures. The condensers appear to be large enough to handle the load too.
If you had a line fail, you will have air and moisture in the system, along with solid contaminants. Make sure you assemble the system with all the seals and gaskets in place. In order to get your air conditioner working again, it will need to be flushed clean with a cleaning solution. Then it will need to be vacuumed down with a vacuum pump. This evacuates all the air from the lines, and also lowers the boiling point of any water that may be in the system, allowing it to boil off. You system will then need to be charged with the proper amount of refrigerant.
Most AC techs fill the system till the high pressure reading in PSI is 2.3-2.5 times ambient temperature. In other words, if it's 80 degrees outside, approximatley 160-200 PSI of pressure on the high side will indicate a proper charge. Another way to check for proper charge is to use what is called superheat. The R134 will boil at a particular temperature when it's at a particular pressure. For example, when it's at 35 PSI, it will boil at roughly 40 degrees. Any temperature above that amount, the refrigerant is referred to as "superheated". Optimal superheat is around 8-10 degrees above the boiling point by measuring the low-side pressure. If you have a very low superheat, your system is overcharged. This is a bad thing, because liquid refrigerant can get into the compressor. Liquid won't compress, and it may damage your compressor. OTOH, high superheat temps indicate a lack of charge. If you have a gauge set, read your pressure on the low side, and place a thermostat in one of the air ducts to compare the temperature too. Locate an R134 pressure temperature chart, and calculate it out.
Using superheat however will NOT indicate other malfunctions in the system, but it is a great way to rule out a lack of refrigerant as being your problem. For example, if your system's low side is at 50 PSI, which gives you a boiling point of around 53 degrees, and your duct temperature is around 62 degrees, your system is properly charged, and your problem lies somewhere else. With this high of a low side pressure, chances are, you have a weak compressor, or your system has been contaminated with air and/or moisture. Contamination can be confirmed by checking your high side. If your high side pressure is high, then it's proably a contamination issue, or even a bad expansion valve. If it's low, then rev the engine up some, and see if the pressures get better.
I DO know that SAAB's have sort of "underdriven" pulley systems, and tend to drive acessories a little weak at idle. This is reflected in AC systems that just don't cool well at idle, an electrical system that doesn't charge very well when under load, and a coolant temperature gauge that gets a little high in warm weather. A lack of cooling power in the city may not be a malfunction...take it out on the highway, and see if it cools better!
...there are many If/Then/or/nor situations when troubleshooting air conditioners. I could write a thread several pages long, but I hope this gives your the basics on where to start in looking for a problem.
posted by 209.158.222...
, Wed, 24 May 2006 20:43:29
, Wed, 24 May 2006 21:49:21, Thu, 25 May 2006 10:11:59
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
