Re: [Chrysler300] Re: 300F A/C Question --- WARNING!!!

["Don Verity" <d.verity@xxxxxxx>]

Hi Roger,
While I also use nothing but R-12, I think your compressor failure was a coincidence father than a design fault. The V-2 compressor is designed to run all the time. It has an oil sump and a tiny little oil pump. Oil level is critical to the life of the compressor. While R-12 and 134 do have different pressure/ temperature rate, they are not that far apart. With the exception of some of the late 50’s  systems, which did have a cycling system, the R-12 systems had a pretty constant low side pressure controlled by the evaporator pressure regulator. The 134 systems used a pressure cycling switch to turn on and off the compressor to control the low side pressure. You can feel the temp change on the older systems when the compressor goes on and off. I think this was done to lessen the constant load on the engine, and increase mileage. The sanden style compressor is also lighter, more efficient, and takes less HP to run. 
300ly,
Don Verity

From: RAKFAR@xxxxxxx 
Sent: Thursday, February 14, 2013 2:15 AM
To: Chrysler300@xxxxxxxxxxxxxxx 
Subject: [Chrysler300] Re: 300F A/C Question --- WARNING!!!

  
Okay, I don't want to pretend I'm an expert (and I didn't stay at a 
Holiday Inn Express last night), but I do have the hard-earned benefit of a bit 
of experience on this subject, and would like to post a word of caution to 
those of you who have yet to travel this road.

Up to a few years ago my daily driver was a 1969 Road Runner 
convertible with factory air (bit of a rare combination). My 300F has 
factory air too, so this is also 300-related. Anyway, after a while the Road 
Runner's A/C got weak, and I determined it needed a recharge. Of course, 
being a 1969 vehicle it required R-12, which was silly expensive and hard to 
find. So after a little internet research and a few phone calls, I fell 
prey to the encouragements of those who said I could switch to modern R-134 
(yes, you can!) with only a few modifications. 

These specified modifications included flushing the system, 
installing new, non-permeable hoses (apparently the R-134 molecules are 
smaller) and O-rings, a new receiver-drier, and R-134 compatible lubricant oil. 
I think all this ran me about $350 or so, and sure enough, while not as 
cold as before, the old Road Runner's A/C worked on R-134.

Or at least it did for about six months, before the compressor 
packed up and died. After much more frustration and investigation, I 
learned a few things: while the mods I made allowed the R-134 to work, the 
basic DESIGN of my A/C system was unchanged. Included in that design were 
certain obscure components like the expansion valve and the EPR regulator that 
(of course) regulated the system BASED UPON TEMPERATURES AND PRESSURES 
UNIQUE TO R-12, and not R-134. Bottom line, as I came to understand it (see 
my first sentence) is that the R-134 confused the poor system, making it run 
practically all the time to maintain its cool. Eventually the overworked 
compressor seized up.

Now, for those of you who live in Michigan or Illinois and use 
your A/C a month or two per year, it may be acceptable ( and may be the 
source of the wives' tale that "you can use R-134 in an R-12 system"), but 
for those of us in Southern California (or Texas or Florida) it just doesn't 
do it.

Take my advice--- if you must have functioning A/C, either 
pony up and pay for genuine R-12, or contact Sanden and get a modern, 
non-original, non-concours R-134 system. Don't say you weren't warned.

300F'ly,

Roger Karlson
Carpinteria, CA

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