Now let me ask you few more questions then.
How do you like R134a? Here in New York City in the summer we are usually at 90-98 degrees + all the heat from the bumper-to-bumper city traffic. Do you think R134a would be sufficient to cool interior down enough?
In a system designed for R12 in your climate or mine (which is cooler than yours, believe it or not) R134a may not perform well for you. It depends on a lot of variables. For the most part, converted R12 systems aren't adequate for "ICE COLD AIR" with R134a because the R12 system, primarily the condenser, are not adequate for R134a. You can change out your condenser to a multipass model to increase efficiency at a cost of about $300 for the condenser.
I am a believer in keeping the system R12 whenever possible. You have some alternatives to that as well through the use of "alternative refrigerants", which is a catchphrase for blended isobutane (propane) that is perfectly suitable for an R12 system. It's cheap and does not harm the environment like R12 does. However, most if not all commercial AC people won't touch the stuff for liability reasons - not because there's a risk of fire or explosion (highly unlikely) but because it's not an approved EPA refrigerant. If you'r still worried about it, understand that it's commonly used as an approved automotive refrigerant in a number of first world countries such as Australia. Our EPA just doesn't like it.
I have used both in my climate, and while the alternative refrigerant does work well, because it's a blend over time if you have leaks, even small ones, the ratio of gasses change as some are more prone to leaking than others due to their molecular size. When this occurs the efficiency of the refrigerant changes because the ratio of gasses is different. You can't just recharge, as you're putting the proper ratio refrigerant into an environment where the ratios are off - you have to evacuate and recharge. Granted, the stuff is about $4/can, so it fairly cheap to do so.
With R134a in a converted R12 system I get 45F vent temperatures at driving speeds. However, when I come to a stop and the compressor speed slows the inefficiency of the condenser comes into play and vent temperatures might rise to 70F. Not a big deal, but definitely noticeable.
If I went through a system and replaced hoses and O rings I would keep it R12. Understand that the hoses on our cars are not what is used today, i.e., "barrier" hoses that prevent refrigerant from leaking out at the molecular level. I can charge a system properly that has no leaks and in a year or so of operation it will need to be topped off. There are no leaks, per se, this is due to refrigerant leaking through the hose medium at a molecular level over time. With newer style barrier hoses there is a physical barrier in the hose material that prevents this from happening.
How often do you need to charge your system with R134a? I've read somewhere when you are converting from R12 to R134a you will need to replace all the hoses and o-rings. It it true?
You don't have to change hoses but it's to your advantage to do so. This is usually beyond the level of the typical conversion, however, as it entails a significant cost and labor to do. O-rings, yes. The R12 O-ring composition will not play nice with the oils used in R134a and they will break down. The green O-rings used today are compatible with both R12 and R134a, so use them and you're covered should you ever decide to convert.
My plan was/is to install new delco style a/c compressor, drier, expansion valve and install BG Frigi-Quiet II oil in it and then take it to the shop to evacuate, leak test and charge the system with R12.
Sounds like a plan, but be sure to put the receiver/dryer on last and make sure the system is closed at that point. Otherwise the desiccant in the receiver/dryer will be exhausted from absorbing moisture from the atmosphere.
I also may have a problem with compressor piping. Rubber hose going from compressor to the hose connected to condenser looks bulging at the ends and also feels soft (see the red arrows in the picture). I think I may have to replace it, but I can't find any reference to it. Any ideas where I may be able to source this pipe/hose?
Mercedes, or better yet, find an industrial hose supplier. They should be able to rebuild your existing hose using the fittings and installing new hose. This is usually far cheaper than buying a new hose.
Cheers! Have a great Sunday![/QUOTE]