Date: Sat, 30 Jul 2005 19:09:50 GMT
From: David Taylor <>
Subject: Re: 1992 saab 900s conv 2.1 ac problem

> line out of the evaporator you can determine the superheat which is a fairly > good indication of refrigerant quantity. In practice many people just > measure the low side pressure and the air temperature and guestimate though. fairly good or correct?, there's a difference. One is correct, the other can be either too little gas and consequently too little lubricant, the other is too much gas and high pressures leading to a stressed compressor and potential premature failure. I know you can get the kits in Walmart etc and i'm sure many people are perfectly happy with them. All i'm saying is that there's the guesstimate/estimate whatever you want to call it and then there's the proper way as specified by the manufacturers which is why the people that do it properly, use scales and not just a pair of gauges. Incidentally, not all cars have a high pressure gauge take off, Volvo 850 for example thus making the top-up concept even harder. FWIW, I recently had my 9000 re-gassed, not that I suspected anything wrong with it, just that I didn't know the history of the A/C and wanted to have a known datum. My usual chap came round and connected the gauges and was pretty horrified by the high pressure shooting round to 400psi and what he thought was an audibly straining compressor. As an experiment, he emptied the system and measured the recovered amount which was 1.2kg when the proper charge should be 950g. Hopefully, i've spared my compressor a premature death. If people want to go ahead and guesstimate, that's just fine by me, it's not my money that's going to go on a new compressor. :) David.

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