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How to: Recharging your A/C - A-Z

Glacier991

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EDIT: BEFORE you start out, see this is NOT an Explorer system and blow it off... stop. The procedures for recharging auto AC are the same (or 99% the same) for ANY system. What you leaern here is 100% applicable to recharging your Explorer's AC!

Recently I posted some info on converting to R-134 from R-12. Many posts since then have involved the aspects of how to properly charge a system. A recent project was the rebuild and recharge of a Sanden based VW bus system. (Sanden AC compressors, best of the best, even Learjet uses em). So in the interests of showing how it *ought* to be done here goes:

The setup... bus engine compartment and vacuuum pump and manifold - the system was rebuilt, and any old parts flushed, oil was added to spec, all we need at this point is to charge it with refrigerant -

15286dscn3624.jpg


The hookup at the compressor blue low/red high -

15286dscn3625.jpg



The vacuum pump -

15286dscn3626.jpg


After a few minutes of running -

15286dscn3622.jpg


On the electronic gauge at the same time -

15286dscn3668.jpg



Running about 20 minutes lowers it even more -

15286dscn3630.jpg


and about 45 mins even more - this is a good vacuum on mobile AC! No moisture or other non condensibles likely to be left in here! Note that we are not vacuuming the system (like a carpet) but evacuating it!!! This is not a process where we are "cleaning out" the system, but rather a process where we are removing all air and moisture -

15286dscn3632.jpg


Ok we are ready for refrigerant. Most important tool ? THESE !!! GOGGLES. PROTECT YOUR EYES !!!-

15286dscn3642.jpg


Ready to charge now. Hooking up the can to the charging hose, haven't punctured the can yet -

15286dscn3643.jpg


Another view, connected and ready -

15286dscn3644.jpg


With the can right side up and gaseous refrigerant ready, loosen this connection and bleed a little refrigerant through the charging hose to displace any air, then retighten it - do this for every new can you attach, you spent a lot of time getting rid of air, don't add it from your hoses !

15286dscn3645.jpg


We start by feeding liquid refrigerant into the "high" or red side, can is UPSIDE DOWN - And open the high side valve - (REMEMBER THE ENGINE IS NOT RUNNING AT THIS POINT - WE WILL NOT START THE ENGINE UNTIL LATER IN THIS PROCESS!!)


15286dscn3646.jpg


The pressures will slowly rise on the high side as the refrigerant is drawn into the evacuated system. The low side gauge will also start reflecting the pressures as they equalize within the system (high and low sides will equalize slowly in a non-running system, so you can see the pressure on either the high side OR the low side once they are equalized) -
Eventually, the first can will empty and a 2nd can, following the above purge procedure, will be started, until the system cannot take any more passively based on can pressurure. The temperature will dictate how much this is, but it's common to get into the 2nd can.... not to worry if it stops half way through, for when we cannot passively feed we can start the system and let it finish the job. Here, we have reached equilibrium pressures without any engine help - this is the low side gauge on the equalized system, easier to see more accurately the pressure on this gauge -

15286dscn3649.jpg


You can see above that the pressure is kinda like the temps on a nice day... good old R-12 closely approximates pressures for degrees F temps. In fact the red band that says R-12 is the temperature band for R-12. Ok, it's time for gas charging, so we close the high (red) side -

15286dscn3651.jpg


Now we are going to charge the rest as a gas. Through the low (blue) side. CAN UPRIGHT and once we get the engine running and the compressor and AC operating, in it goes -

15286dscn3652.jpg



As we start the engine. the high side will rise and low side will start to fall... he's the low side before we start adding gas with the engine operating the compressor-

15286dscn3655.jpg



We open the valve and start adding gas (can upright!)and the pressure jumps.

15286dscn3657.jpg



Why ? Because the system low side pressure is equalizing to can pressure, but taking it in at the same time, it will start to drop soon -
eventually the cooling can (yeah that sucker will get cold!) will again equalize pressures. You can speed things up by adding the can of refrigerant to hot water in a coffee can or similar, like this -

15286dscn3656.jpg


Once you do this the low side will jump again, but soon lower once the rest of the gas is drawn in. Here is the final charge on this system on the gauges -

15286dscn3659.jpg


Now to disconnect the gauge set. With the engine and AC running I disconnect the low side, and - this is important - add the cap, the schrader valves are a weak link in system leakage and caps really DO help!! - just make sure the rubber o-ring is inside and intact. Mineral oil it if you have some, that adds another barrier.

15286dscn3660.jpg


I leave the high side connected as I stop the engine -

15286dscn3661.jpg


The high side will SLOWLY bleed down from a HIGH pressure - time varies but wait til it is at a low pressure, this was after a few minutes, give it time - it can take a while to equalize, but be much easier to disconnect -

15286dscn3662.jpg


Last thing to do is to check for leaks. I use this sniffer to check for leaks, here at the compressor connections -


15286dscn3664.jpg


And at the main compressor seal, for the record I check underneath too, this was for photographic purposes... -

15286dscn3665.jpg


I'll also check wherever else it might be appropriate. So that done, the job is finished. In this case I knew exactly how much refrigerant to put in, if this was a top up I'd be watching low side pressures and monitoring vent temps more closely.

There is a big benefit of deep vacuum and taking a long time pulling a vacuum before you start; purging hoses to eliminate air and importantly wearing goggles. I kid you not, your eyesight is worth it, and I'm not being a woos. Please do it.

I hope this added something to our collective knowledge.

Happy, and cool, Exploring

Chris
 


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viiidude

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Very nice post! Appreciate the pics.
 




Sir Robin

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Can you give us a rundown on what each piece of your equipment costs? The gauge set, vac. pump, "digital" vac. gauge/indicator (CPS gauge), and leak detector.

Also, I know you are careful about handling the refrigerant and keeping within the law. How do you know when the charging hose has been purged of the air? By smell, by sound, by time? I guess you can't avoid letting a tiny bit of refrigerant leak to the atmosphere during this important step.

What about putting an extra valve on the end of the line? This way you can evacuate the line with the rest of the system, and then close it to preserve the vacuum as you take the hose off the vac. pump and hook it up to the can? (Even just use the same valve that goes on top of the can?)

Lastly, you are highly regarded on this board as an a/c expert. Is refrigeration your job, or at least part of it? Or is it something you do on the side?

Thanks.
 




Glacier991

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Robin... No I'm no longer doing AC for money, but I still do it on the side. I got interested in it years ago and still enjoy helping out others.

You are most correct about the hose end shut off. I debated posting that, (which technically you should have on EACH hose end) but wondered how many people would have those. The "perfect" way is just how you suggested, and once you are done you close all 3 valves, trapping refrigerant in the manifold and hoses. Then you hook it up to your recovery machine and recover the refrigerant from the hose/manifold set. Technically that is the law. I probably should have performed it in that way, but was afraid to scare off someone seeing me hooking up a recovery machine just to charge a system.

As for tools... just to give you an idea, and one certainly does not need this extensive a list -

I have a couple of vacuum pumps, I paid between $200 to $300 for them apiece. The gauge set is one of several, I think I probably paid $50 to $75 for it. The "sniffer" is something I picked up on E-bay for $50 or so. Same with the digital gauge, although I think I may have paid closer to $75 for it. I have an air powered flush gun (about $60 I think) and a refrigerant identifier (used E-bay for $200). I have a charging scale (for when you use jugs instead of cans, it reads in 1/4 oz, and I paid about $150 for it. Throw in a couple hundred bucks worth of compressor tools, temperature gauges and the like and that's about it, save the recovery machines..

I have a recovery machine (a Robinaire 25175 I paid about $275 for, and a recovery/recycle/reclaim machine - a Robinaire 17500B I paid about $400 for. It's main limitation is that it cannot recycle 134a from PAG oil systems - which is why I got it so cheap. I also have several tanks for recovery - 1 for R-12, 1 for R134 and one for R-22.

Overall I suppose I have around $1500 to $2,000 in AC specialty tools, but so far this year alone I have had to do 3 of my cars (2 total rebuilds) one for a friend, and 2 residential installations. The labor savings this year alone would have bought these tools. Over the years the tools have easily paid for themselves many times over.

Hope this answers your questions.

Happy Exploring

Chris
 




Glacier991

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Several folks have written asking me how to find a reputable shop to do their AC - while they enjoyed the post, they don't want to do it themselves, which I respect.

So, that said how DOES one find a good AC shop? I can offer no real easy answers but can offer my observations. Doing mobile AC requires certification - it's not hard to get really, but not every shop always has someone around who is certified. Many dealerships for example contract out their AC work for just this reason.

My personal preference is to go to a shop that more or less specializes in Auto AC. Few can afford to ONLY do AC - they'd starve in winter, but see if it is a major aspect of what they do. How do they keep their shop? A neat clean shop says a lot to me. Ask ahead of time for an estimate - keeping in mind that with AC you often do not know the true extent of necessary work until you get into it. Ask about a warranty - how long will they stand behind their work? And, go with your gut instinct. If the workmen seem confident and know what they are doing, and you get a good "vibe" you probably will be a happy camper.

One thing people tend to forget is that it costs money to run a shop and pay wages. A shop rate of $50 to $75/hr is not unreasonable. There is little one can do to an AC system in much under and hour start to finish. Refrigerant will cost based on the type. R-12 is at least $25 a pound, R-134 should be closer to $5-8 a pound(or less). You might ask their charge for rerigerant and see if they are trying to charge you $20 a lb for 134 for example. I do not mind a mark up for handling refrigerant, but there is a limit. Ask if there is a fee should they need to recover your old refrigerant. Will they reuse it if they do or add new? (valid reasons may exist NOT to simply reuse the old, and they should charge you for it if they use new.)

I hope this is useful.

Cool exploring

Chris
 








ve4ron

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Great thread just had to bump it .
 




ve4ron

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Tis the season to bump this thread .
 




Eneurb

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It was such a long post, I may have missed a few parts. I thought that I might add that when converting from R12 to HFC134, it is a pretty good idea to replace your accumulator or reciever drier while doing the conversion. Some R12 accumulators have a desicant bag that is not compatible with HFC134. Just a suggestion... great post!

Oh, and ester (polyolester) oil is a great substitute when doing a conversion as it is compatible with both PAG and mineral oil, but unlike PAG it isn't water soluble, so it helps make leaks more evident if the occur.
 




Glacier991

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Eneurb thanks. I "think" I covered that, if maybe only in saying on a retrofit change the accumulator.... but as usual you offer sound advice... an older model may use dessicant suitable only for R-12. Recent models use dessicant useable for either. Replace the accumulator!

Also I use Ester based flush and use ester on my convesions. Thanks for pointing out the benefit.
 












Glacier991

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And finally a new forum home AC issues !
 




Garth

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Is there a pic or diagram that shows the valve to recharge ac?

I am actually searching but have not found that info. Will continue to seach.

A short cut would be nice still.

Thanks.
 




BrooklynBay

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Take a look at the above pictures. You could see the charging hoses connected to them with a manifold gauge set. I have a question. If an R12 system had the possibility of being converted to R134A from the previous owner, but has no updated R134A fittings (might have been removed after being recharged), would R134A do any damage if added to R12 just in case the system still had it?
 




Garth

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I am using a single can of autozone stuff which comes with a snap on connector. The connector cant fit on the valve next to the radiator.
 




shamaal

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BrooklynBay said:
Take a look at the above pictures. You could see the charging hoses connected to them with a manifold gauge set. I have a question. If an R12 system had the possibility of being converted to R134A from the previous owner, but has no updated R134A fittings (might have been removed after being recharged), would R134A do any damage if added to R12 just in case the system still had it?

The R12 mineral oil does not dissolve well in R134.
http://www.epa.gov/Ozone/title6/609/technicians/retrguid.html
 




BrooklynBay

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Thanks for posting that link! It has a lot of useful information. I guess if there is a doubt about what is in the system, it is better to evacuate everything, and start over with R134A. I remember before they had R134A that there was something being sold called "R12 substitute". It was supposed to be capable of being mixed with R12. It was only sold for a short time. Somebody that worked in an auto parts store told me that it was destroying A/C systems, and it was taken off of the market.
 


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Glacier991

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Shamaal is correct - the term for dissolvability of oil is called "miscability". R134 will not (for all practical purposes) carry mineral oil, because of the low miscability of mineral oil in 134. This is discussed in the Converting your R12 system to 134a thread in the stickies. Interestingly, mineral oil does form a barrier to the smaller 134 molecules so is a good bet for lubricating 134 system seals and even hoses prior to use. (I still prefer NYLOG as a O ring/seal lube though).
 




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