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Old 05-21-2014, 11:49 AM   #1
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Default Boring AC Question

I know, most of you gays don't even have A/C. I'm in AZ and it's already been 105 a few times now.

So I'm really considering keeping A/C in my car. The issue is, it has been open to the atmosphere for god knows how long. It could be 10 years for all I know. It was disconnected at the compressor. I plan to replace the compressor either way, as it looks beat and doesn't spin that well. Plus they are the only A/C component readily available for the car at a decent price.

My question is: How much of a chance is it that the whole system is garbage from being opened to the atmosphere for so long? This is my 76 BMW I"m talking about, so I can't exactly just get more A/C parts, they didn't even come from the factory with A/C. I'd rather not spend a million dollars at a shop having them replace a million things, and molesting my beautiful car. So what do you guys think NEEDS to be replaced on the system?
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Old 05-21-2014, 12:53 PM   #2
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Originally Posted by FRT_Fun View Post
I know, most of you gays don't even have A/C. I'm in AZ and it's already been 105 a few times now.

So I'm really considering keeping A/C in my car. The issue is, it has been open to the atmosphere for god knows how long. It could be 10 years for all I know. It was disconnected at the compressor. I plan to replace the compressor either way, as it looks beat and doesn't spin that well. Plus they are the only A/C component readily available for the car at a decent price.

My question is: How much of a chance is it that the whole system is garbage from being opened to the atmosphere for so long? This is my 76 BMW I"m talking about, so I can't exactly just get more A/C parts, they didn't even come from the factory with A/C. I'd rather not spend a million dollars at a shop having them replace a million things, and molesting my beautiful car. So what do you guys think NEEDS to be replaced on the system?
I'm certainly no expert, but my limited understanding is that you'll likely need to replace the dryer (usually a cylindrical canister attached to or near the condenser) if it's been open to atmosphere for any amount of time. Beyond that, you'll need to have the system professionally charged, as they'll need to pull a vacuum before adding coolant.
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Old 05-21-2014, 01:14 PM   #3
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Replace compressor and receiver/drier and add fresh oil if compressor was shipped dry. Vacuum to test for leaks. If it holds the vacuum then recharge. If not, find the leak(s), repair, and recharge. It isn't rocket surgery.

I have one of these to make it easier:

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Old 05-21-2014, 01:36 PM   #4
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The receiver/dryer seems to be a common part as well, so I'll grab one of those with the compressor. Throw it all back together and then have a shop see if it holds vacuum and go from there.
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Old 05-21-2014, 04:39 PM   #5
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Having been open so long in a dusty environment, you might want to find a shop that can also flush the system prior to doing the final evacuation and charging.

I'm trying to picture an AC system for a '76 Bimmer. Underpanel add-on type system?
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Old 05-21-2014, 04:40 PM   #6
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Oh, we need pics of your 2002 also. Always liked those. A lot of greenhouse though -- that would be rough in AZ.
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Old 05-21-2014, 05:37 PM   #7
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Oh, we need pics of your 2002 also. Always liked those. A lot of greenhouse though -- that would be rough in AZ.
I have a build thread. Title was edited in the ceremonial MT.net fashion. Not actually a part out (yet). I think you can see the A/C panel in some of the pictures. Two big vents (and 2 small ones on either side). From what I hear the BEHR system that I have was installed as a dealer option and looks the most "OEM". It also is rumored to work very well if set up correctly.

https://www.miataturbo.net/build-thr...-thread-78759/
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Old 05-22-2014, 08:52 AM   #8
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With it sitting open that long I would definitely flush the system and replace the filter/dryer before doing a vacuum leak test. If possible remove the condenser and evaporator and do a flush off the car so you can move the cores around and rinse all dust/debris out. This will also give you a chance to find any metal shavings from a old compressor that took a crap. These shavings will kill a new compressor. If you know there weren't issues with the compressor when it was disconnected, you might be OK.

What kind of refrigerant does this old system use?
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Old 05-22-2014, 09:34 AM   #9
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It would have been an R12 system. Just put in 134A and .
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Old 05-22-2014, 09:50 AM   #10
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Just happen to be in the middle of AC research for the Miata and my 87 Benz. If you go with the r134, I'd update the condenser to a parallel flow because your current R12 condenser is probably a tube/fin, which sucks for 134. I found this on eBay. As stated- flush, new o-rings, and then pull vacuum. A fan upgrade will also improve the efficiency with 134.

Another from Shepherd
Amazon.com: Shepherd Auto Parts OEM Style Air Condition AC A/C Condenser Condensor: Automotive Amazon.com: Shepherd Auto Parts OEM Style Air Condition AC A/C Condenser Condensor: Automotive

Parallel:
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Old 05-22-2014, 12:19 PM   #11
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Problem here is I need to use (especially parts like the condenser) as many of the old parts as possible. If you have been in the nose of a 2002 there is very little room to play with. The parts I have now bolt up to factory locations. I don't want to fabricate, or put a bunch of money or work into this. If it comes to that I"ll probably just shelf the system and come back to it at some other time.
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Old 05-23-2014, 05:22 PM   #12
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Ive had several Miatas that come in with systems that have been sitting open for years. I run 1 or 2 cans of something like this through it, and then use compressed air to blow the remaining fluid out of the condenser. I've noted a fair amount of sediment comes out of certain condensers, so I might be worth it depending on your environment.

Other than that, replace the o-rings where necessary, replace that compressor and dryer and see if she holds vacuum. There's R12 still out there, and some substitutes I've heard of are not propane based, and are more efficient to use than R134 in a R12 condenser. Good luck! 105 degrees sucks.

EDIT: I've also run some of the flush through evaporators where owners had detached the lines at the fire wall. The stuff is supposed to be citrus based (I think) and hasn't had any adverse effects on systems as far as I can tell.
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Old 05-27-2014, 03:13 PM   #13
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If you're stuck with R-12 (no serpentine or parallel flow condenser or evaporator) use Freeze 12. It's a refrigerant blend, so no one will want to touch it when you're done, but it works great. I put it in my Camaro before I tore it apart and turned it into a project.

You need a government license to order it online, but IIRC, the test is $25 and laughably easy, and Freeze 12 was cheaper than R-134a.
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Old 05-27-2014, 03:15 PM   #14
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At this point I'm ditching the A/C. This car has a pretty damn good flow of air coming in at cruise. Stop and go is a bitch but I'll survive. In a year I plan to get a decent daily driver with A/C so that won't be a problem.

Thanks for the heads up though.

PS I might be moving down your way soon.
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Old 05-29-2014, 06:13 PM   #15
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Just make sure your window regulators dont go out. That happened to me after I deleted mine. South Texas summers with no a/c and a broken driver side window reg suuuuuuucks.
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Old 05-29-2014, 07:59 PM   #16
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Just throwing this out there- I have several cans of genuine R12, and several more cans of pre-ban R12 compatible refrigerant w/ oil and stop-leak.

I'd be willing to make a deal.
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Old 05-29-2014, 08:09 PM   #17
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How effective is stop-leak in a/c systems? I know its a big no-no in radiators.
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Old 05-29-2014, 08:35 PM   #18
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It works about as well as head gasket repair in a can. Don't use it. It will only cost you more when it comes time to fix, especially with newer cars that use parallel flow condensers. Any buildup is impossible to flush, which means new condenser. NB's have parallel flow evaporators too....

If you have a leak, fix it. It's an o-ring, seal, or a pinhole in a hardline.

I'm probably going to recharge mine with a propane/butane mix from Envirosafe Refrigerants. They've been doing it in Mexico and Cuba for years and it's about the same amount as what's in the small camping tanks at Walmart.

It's supposed to require less pressure, which means less a/c load for the same performance.
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Old 05-29-2014, 09:09 PM   #19
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^Thats what I figured, but Im no a/c tech.

The propane/butane info is interesting. I dont have an a/c system in my car anymore but my wife's type s does and it may need a recharge soon.
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Old 05-29-2014, 09:56 PM   #20
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Quote:
Originally Posted by FRT_Fun View Post

My question is: How much of a chance is it that the whole system is garbage from being opened to the atmosphere for so long? This is my 76 BMW I"m talking about, so I can't exactly just get more A/C parts, they didn't even come from the factory with A/C. I'd rather not spend a million dollars at a shop having them replace a million things, and molesting my beautiful car. So what do you guys think NEEDS to be replaced on the system?
Alright my friend, first things is first. YES, damage MAY have occurred to the system as a result of atmospheric contamination. The main component to worry about is the orifice tube, which allows the compressed refrigerant to be released under pressure, change phase, and absorb energy at the same time. However, the odds that it saw significant damage are low.

Second, R12 is not required. 134A runs just fine in R12 systems, with a few adjustments. First, you'll need a set of R12 to R134A adapters for the machine.

Amazon.com: ATD Tools 3525 R-134a Coupler Conversion Set: Home Improvement Amazon.com: ATD Tools 3525 R-134a Coupler Conversion Set: Home Improvement

These should not be left on the car after the service is performed. You'll also need the spec refrigerant weight for the system, using the R12. Subtract about 20% of that weight, and that's the "correct-ish" amount of 134A to use.



When replacing the compressor, you'll need to replace the receiver/dryer, and if the orifice tube is easily assessable, do it too. Most shops will have an o-ring assortment, but if you can find a set, buy it just in case. Remember to oil the compressor before installation, with the correct spec oil, and turn it by hand to flow the oil throughout the pump. Get a mixing cup with fluid ounces increments, and feed it into the low-side port. Most pumps recommend 10 complete turns. I do 25. Lots of pros kill brand new compressors, because they tried to skip that 5 minute step. They typically only make that mistake once.


When driving to the shop, the system will obviously have atmospheric air present. Do not run the compressor. Until it has been properly serviced and vacuumed, damage may occur. You'll do 3 main vacuums. First down to 20hg or so. It will likely chug and work for minute or two to hit that. Let it sit for 5 minutes or so. Then, hit it for for 30minutes, continuously. Afterwards, you should be in the 26-28hg area (gauges often read a tad high). Let it sit for 15/20 minutes. If pressure drops more than 1hg, you have a leak. No-biggie though, the system must have a 134a charge to function and circulate the dye anyway. After sitting, run vacuum for another 5/10 minutes, then charge. Always make sure to inject your dye (1/4 inch on most dye-gun scales is plenty). Brake clean will remove any spilled dye around the low side injection site. I recommend doing this will the car is running, as it takes the dye much easier.


Then fire the bitch up, and enjoy the AC.



Check in a week or two with a UV light for leaks. No need to break out the manifold gauges. As for AC-in-a-can, and "stop-leak". You'll ruin the system, period. Refrigerant and oil are ALL that should be in the system. Dye isn't really supposed to be in the either, but it doesn't have the hydro-carbons and adhesives the AC-in-a-can **** does.





And **** those fancy Robinair machines. Find an older guy, likely at an indy shop, with an older machine. I love my machine, and it's at least a decade old. Mechanical valves and standard switches.
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