91 740 A/C Retrofit Help Needed

Another one for the A/cC experts. I need to "finally" recharge my A/C system
but I want to go to the R134a. first question; Is it okay to do so on a 740?
Next question; Where, or should I ask, which ones are the fittings for the
low/high side? TIA

 

moster ha scritto:

I am doing it on my 91 940 with B204E.
You need to replace the accumulator, the expansion nozzle and charging
connector, plus some O rings.
Then you should empty all of the oil into compressor and to put the
specific one (ester oil only).
Practically you need this Volvo conversion kit (p/n 9145660):


http://www.fcpgroton.com/images/9145660.jpg


good work and excuse for my english, I write from Italy.
Paolo.

 

This seems like it might be a job for a real A/C guy. Anyone ever done this
on their own?

 

No, but I learned fast not that R134a is much harder to work with than R12.
I'd definitely seek out a real A/C guy. I had the dealer do the upgrade on
our '85 when the old compressor seized; with a new compressor the total bill
was $1100 or $1200 US about 10 years ago.

You should look into just getting it serviced with R12. The stuff is
expensive and getting rarer, but R134a doesn't cool very well in a system
designed for R12. At least ours doesn't, and I've heard similar complaints.

Don't worry about the ozone. A decade after the US signed the Montreal
Protocol that doomed R12 production, NASA and NOAA conducted a joint mission
called POLARIS to determine just what was causing the seasonal ozone
depletion that had everybody stirred up. Their conclusion as to the actual
cause, in the words of the End-Of-Mission statement, was "... periods of
prolonged solar illumination such as occur at high latitudes during summer."
We can thank politicians for another snafu.

Mike

 

Sure, I did it on my 740 and I've done it on a few other cars since, the
process is pretty much the same. Volvo offers a retrofit kit, get it, it
will make your life much easier. You'll also need to remove the compressor
and empty out any existing oil, flush the hoses with refrigeration solvent
to clean the oil out of them and then replace all the O-rings at every
joint, the filter/dryer, expansion orifice tube, and you should change the
pressostat on the filter/dryer since it's a common failure and it's cheap.
Once you do this you need to use a vacuum pump to evacuate the system then
finally you can charge it up. Real vacuum pumps are somewhat expensive but I
use a salvaged window AC compressor and it works better than the real vac
pump I borrowed once. Another option is to do the conversion then take it to
a shop for the evac and charge, just make sure you do this immediately after
installing the new filter/dryer or moisture will get in and ruin the new
one.

 

Why's it any harder? The conversion on mine took an afternoon, it was a
little slow the first time since I'd never touched an AC system before, cost
was about $200 from start to finish. How is R12 any easier? I dreaded the
difficulty or expense for years, then I just dove in and did it and was
pleasantly surprised at how simple it turned out to be.

 

In theory at least, conversion isn't any harder (assuming having a vacuum
pump available in either case. Remove what's there, including oil, evacuate
for 30 minutes, add the right amount of oil and refrigerant and Bob's your
uncle. It's the recharge that isn't nearly so easy. With R12 I could
recharge by sight glass if available, by guages or by ear (listening to the
compressor cycling.) All would give satisfactory results. I had heard that
R134a required recovery and measured charge to work but I figured that only
applied to newbies, not to an old hand like me. Hah! I tried to recharge my
son's 134a system by guage and ear, going very slowly so I wouldn't
overshoot. After half an hour the evaporator pressure hadn't come anywhere
near the target, the compressor was still cycling like it did originally and
I started to hear little slugs of liquid hit the compressor. We shut it down
and I had him take it to an expert. We were about 6 oz overcharged, and once
the system started with the correct charge it worked perfectly with no
cycling at max load. Why it behaves like that I don't know, but I learned my
lesson.

Mike

 

I just dumped in 3 cans from empty and it worked like a charm. In reality it
should have had just a tad more according to the charge weight it specifies
but 3 can is close enough. If you want to get it just right, use a postage
scale the weigh the fourth can and you can get it spot on, if I lived
somewhere really hot I'd do that but mine works fine for the typical high
70s summer day.

Charging by looking at the sight glass or guages alone works for a system
with a TXV like most older systems used, but the 740 has a fixed orifice so
you'll WAY overcharge it if you fill it until the sight glass doesn't have
bubbles.

 

We were doing it on an Acura - no sight glass, not a conversion.