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

Reply to
moster
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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):

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

Reply to
Telespalla Bob

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

Reply to
moster

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

Reply to
Michael Pardee

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.

Reply to
James Sweet

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.

Reply to
James Sweet

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

Reply to
Michael Pardee

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.

Reply to
James Sweet

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

Reply to
Michael Pardee

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