A/C System Recharge Guidance - LotusTalk - The Lotus Cars Community
 
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post #1 of 9 (permalink) Old 04-30-2019, 05:27 AM Thread Starter
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A/C System Recharge Guidance

My S4 is fitted with a Senden A/C compressor. The system worked fine before the engine pull, so I have no concerns over leaks, though we'll check during the refill process. As you can see from the photo, there are 2 ports identified on the compressor as 'SUC.' and 'DIS.'.

There is an in-line fill port accessible under the car but it is in the 'DIS.' line. I am assuming that the 'SUC.' port is for filling the system? (suction?).

I likely have this all wrong. BTW, I've located a stash of R-12 that I'll be using to fill the system per an earlier discussion on the forum. I'm heading to Harbor Freight to pick-up one of their vacuum pumps.

Any help or guidance is appreciated.

Thanks!
Bob
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post #2 of 9 (permalink) Old 04-30-2019, 05:35 AM
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Cant help with your question but I will be eagerly learning from you.

One tid bit - A shop owner once told me that the big expensive AC machine he used could do things that you cant do as a home mechanic with a set of gauges and a vacuum pump. I cant recall the specifics but it made sense at the time. It was a car I did not want to work on any way so it was the excuse I needed.

Another thing. Since many of our cars are switched over to 134 - including mine I noticed something the other day in the parts manual.

The post 95 cars have a dual pass AC condenser and were designed to run 134. Our cars have a single pass and originally came with R12.

If we convert to 134 but dont add the dual pass AC condenser how much performance are we losing? Would it be worth it to install the later condenser?

I know my AC even with a fresh charge is not that great and I hear lots of folks say the AC was never that great. But I also hear folks that are happy with it.

94 Esprit S4 - Silver
Previous - lots of hot rod Air Cooled 911s
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post #3 of 9 (permalink) Old 04-30-2019, 05:52 AM
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You fill on the low side.

i would look in the shop manual and see where the fill port is, not usually on the compressor
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post #4 of 9 (permalink) Old 04-30-2019, 06:11 AM
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Although I consider myself a thoroughly competent Esprit mechanic I leave all AC charging, diagnosing, repairing to the AC guys at my local shop. The equipment a modern AC uses is complex and incredibly expensive (the reclaim machines I have seen advertised on tool websites for example go for $12,000 and up). You need "sniffers", you need dye, you need UV light sources, etc. Although I generally don't have anyone else do any work on my '89 I'm happy to turn it over to the AC shop when it needs AC attention.

And if you are discussing a car that was originally an R12 refrigerant car, then you will lose about 20-25% cooling capacity by just dropping in R134. I have always kept my car in R12 because of that and the AC does a credible job even in sunny Florida. R12 is still legal if vended by a licensed shop. What has stopped is the manufacture of R12 so there is still old and reclaimed stock out there if you want to stay in the R12 mode. It is more expensive than R134 but not prohibitively so - my AC shop said R12 adds about $80 to the cost of a refill of my system.

Tom Mieczkowski
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post #5 of 9 (permalink) Old 04-30-2019, 08:46 AM
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Good advice above. The A/C shop I use has a much better vacuum than I'd be willing to buy and that's important both to help test for leaks and also be sure you have 100% of the moisture out of the system. Also be sure to replace your drier as those should never be reused once the system has been opened. Remember too that if your car was retrofitted with R134 then the Schrader valves will likely have been changed to a different size (as is required) and if the conversion was done properly the oil was changed too. If you're going back to R12 both of those things will need to be reversed.
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post #6 of 9 (permalink) Old 04-30-2019, 11:02 AM
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Doing A/C work requires some special tools and they can be expensive especially if you are only doing your own car. Like glass work, or alignments, it really doesn't pay to do it yourself. That said, if you still want to do your own A/C work you will need a manifold gauge set and a vacuum pump at a minimum. You can get by with an air compressor but you really should use Nitrogen. Connect your gauge set to the car, blue (low side) to the suction (large hose) and red (high side) to the discharge. If there is any pressure over around 20 psi you should reclaim the gas. Assuming it is flat you pressurize to 100 psi and check for leaks. Once you find and fix any leaks, you replace the oil, dryer, and service valve cores. Vacuum the system and refill with the correct amount of refrigerant. Performance test the system and see that it makes water and it comes out. Stay with R-12 for as long as you can. Anything else and you lose some capacity. That goes for -134 and any of the blended substitutes. The system was sized and designed to perform with R-12 and anything else just can't do as good a job. If you do convert you must change the service fittings and label the system so no one puts the wrong stuff in. This is the very abbreviated procedure, there are a lot of little things that get done (or at least should be done) to do this correctly. Messing up and you can damage a lot of expensive parts and worst case you can also damage yourself. Liquid refrigerant on your skin or eyes will freeze them instantly. It is easy to hook up wrong and over pressurize those little R-12 cans and they will explode.
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post #7 of 9 (permalink) Old 04-30-2019, 11:25 AM Thread Starter
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Well, those are a lot of very creditable opinions weighing-in on my question! I have not converted over to R134; it is still a R12 system, and per David, I intend to keep it that way as long as supplies last because of the documented effectiveness.

Question is: will A/C shops work on R12 systems? And the latent question: how much? I'll let everyone know what I find out.

As always, thanks for the kind replies...couldn't do much of this without the community.

Bob
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post #8 of 9 (permalink) Old 04-30-2019, 05:36 PM
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Some shops will not work on -12 systems anymore unless you allow them to convert. Be sure to mention that right up front that you want to stay with R-12. You should be able to find one if you look. Also mention that you have the R-12, they may not want to use yours or they may not want to do it unless you have it. A small independent shop is what you want. Chain type shops will not do it. If you can, find one that specializes in old cars. The A/C system in a Lotus is nothing special so any shop that can do car A/C should be OK.
David Teitelbaum
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post #9 of 9 (permalink) Old 04-30-2019, 06:26 PM
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A good radiator and A/C specialty shop should be able to handle it. My '73 E-Type has R-12 and I've had no problem getting it recharged over the years at a local (SF Bay area) radiator shop and the cost was maybe $50 - $75 more than a "regular" charge. The labor is the same. There's no magic to servicing an A/C system so any good quality shop should be able to handle it if they have the right equipment and are willing to work with R-12.
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