Mike Puckett said:
I called an A/C shop today and the cost of R12 is about $4.50/oz. For the 32 ozs that the system holds that's $144 just for the freon. Yesterday cruising at 40mph with an outside temp of close to 90 and my window halfway down, the thermometer stuck in my center vent read from 46 to 51`. I've been wondering how well that smaller condenser coil works.
Well you certainly did the right test. That would be mediocre to not great performance. Most shops would say it doesn't quite meet specs since its about 40 degrees below the outside temp, but if they don't care about your business, they'll say its fine
They generally state that 50 is the standard. You wouldn't be real happy if it were 100 out, although Max A/C (recirculate) would get it colder.
Mine is hitting 44 from 95 outside on norm and 40 on recirc and that's with r134, a 6mm serpentine condenser, and a few oz of refrigerant missing due to a slight blunder on my part when taking some pressure readings.
I intend to tune it later as I think 39 is achievable.
Also, the 90 holds 40oz of r12 and the rule of thumb is 80% of that for r134 which is 32oz. So for $180, it might be worth the conversion, but factor in another $150, or more, for an upgraded condenser to get better than mediocre cooling and you can see that retrofits aren't necessarily any cheaper. The condenser really is optional but much less optional if the compressor blew.
Usually, you want as big of a condenser as you can get and a tight set of small diameter coils which run in 2 or more parallel paths. The original r12 condenser is a tube and fin with bigger coils and 1 split path. It works
great with freon.
I'd be curious as to what a shop charges for new orings, new accumulator, flush, vaccuum, fill, and the cost of the refrigerant which is what a reasonable job would include.
Anyways, most of the decision is up to the owner. There are low cost quicker ways that have a track record of killing A/Cs (the pros call them compressor death kits) and there are higher cost ways which aid the longevity of the compressor. Now factor in that a pro probably would discourage the kit cuz that's their business, but there are a few that say that the only way they'll warranty their work is if its done a certain way and none of them expressed any desire to do rework.
Due to a number of factors, mostly wanting to preserve my compressor warranty, and the cost and time of the job, I chose to do the full up job. In my case, my old compressor had siezed up.