Hey everyone. I'd like to get my AC working properly again. At the moment, it's just wimpy, and the drier isn't frosting up like it used to.

I'm pretty sure it's low on refrigerant, it DOES cycle, but only gets cold when I run the car hard. Engine rpm doesn't seem to matter, but accelerating fast or changing the engine rpm quickly does matter.

Anyway, assuming it's low on refrigerant, I plan to top it off with autofrost, not do a whole retrofit. A lot of R-134a can-taps have pressure gauges on them.
I'm not going to buy a $100 manifold gauge set, so I'm looking for a cheap way to check the pressure. If it came to it, I would do a whole autofrost/R406a conversion, not the R134 conversion.

Here's what I'm thinking:
1) Find a cheap R12 can tap that measures the pressure.
2) Buy the R12-R134 fitting adapters and hook up an R-134a can tap (with a gauge). The adapter and gauge-tap would be something like $25 at walmart.

With option 2 - would the pressure be right? Pressure is pressure, right? Also, could I tap any can with it? If I get a side tap, I assume I could.

Happy Bricking,
Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond

I read somewhere that the AC system needs a specific amount of freon, even describing it by weight.
I am not well versed in adding freon - never really done it personally, but I do know that when I took the wife's 940 to a small shop that supposedly was Volvo savvy - the apparent adding of too much freon created an excessive pressure situation that eventually killed the compressor. I can't even begin to describe the sound it was making, but it sure was cold in the cabin, so it was left that way for way too long, long enough to kill the comp.
--
' Of all bad men religious bad men are the worst. '' (C S Lewis ; on Evil Men) 89 764 (170K), '94 940T (265K), 92 245 (150K)

Hi Will,

Before messing with your precious R12, try simply cleaning the condenser and radiator. The dependence on speed and engine performance leads me to guess the condenser fins might be in need of a hose down.
--
Art Benstein near Baltimore

My wife has a slight impediment in her speech. Every now and then she stops to breathe. - Jimmy Durante

I don't think anything like a "cheap can tap" exists for R-12, since it was never really legal to sell to consumers. Also, you'll never find a way to get R-12 through a 134a tap; The EPA has a law that these adapters can't exist. Finally, there's the law of partial pressures, in that the total pressure in the system is just the sum of the pressure of the two gasses. Which is what matters: You won't have enough 134a or R-12.


Best thing to do is just convert the system. Not too painful or expensive to do once you get the R-12 collected. If you were closer, I'd lend you my pump and gauges.

-Ryan
--

Athens, Ohio
1987 245 DL 314k, Dog-mobile
1990 245 DL 134k M47, E-codes, GT Sway Bars, GT Braces, Draco Wheels
1991 745 GL 300k, Regina, 23/21mm Turbo Sway Bars

One used to be able to buy cans of R-12 at Kmart. One refill kit I have includes the fill valve which pierces the can and allows it to flow into drier.

I have all of the above. The kit even included an attachement to blow off extra R12 into the environmant if you put too much in.
--
Paul NW Indiana '89 740 Turbo 140,000

I don't think anything like a "cheap can tap" exists for R-12, since it was never really legal to sell to consumers.

Hi Ryan,

You make me feel pretty old.
--
Art Benstein near Baltimore

What would men be without women? Scarce, sir... mighty scarce. - Mark Twain

Uh oh. I'm guessing R-12 was available before it was unavailable? :-)

Sorry...

-Ryan
--

Athens, Ohio
1987 245 DL 314k, Dog-mobile
1990 245 DL 134k M47, E-codes, GT Sway Bars, GT Braces, Draco Wheels
1991 745 GL 300k, Regina, 23/21mm Turbo Sway Bars

No need to apologize. Mrs B will tell you I am old.

I think Will remembers when this was a common sight in summer driveways, and as casually treated as changing an air filter. Fill 'er up until the bubbles disappear in the sight glass. This ancient Daguerrotype I borrowed from the historical society to scan, depicts (minus the scale) a typical shade tree weekend activity back when the R12 cans were sold next to the Pennzoil in the Western Auto store.




--
Art Benstein near Baltimore

Only Irish coffee provides in a single glass all four essential food groups: alcohol, caffeine, sugar, and fat. - Alex Levine

Nice scale. Do you have one to recommend? I also need to weigh the cans while they are inverted and charging the AC system.
--
john

Sorry John,

Meant to reply, and forgot until Andrew bumped the thread again.

I was using the i5000-H I normally use for making bread and coffee, from myweigh.com. Don't know that I would recommend it. I chose it for its 1-gram resolution. Its selling feature seemed to be it was made from hemp plastic, but I happen to like longevity in my plastic (i.e. wiring harnesses) over bio-degradability. Surely this $50 item, if sold purpose-made for HVACR would have cost $250.

Something better certainly exists nowadays.

PS - if you want a laugh on product use warnings, glance over the i5000 manual here.
--
Art Benstein near Baltimore

If you lend someone $20 and never see that person again, it was probably worth it.

I believe I once saw R12 for 77 cents a can at Kmart.

Thanks for all the replies.

-Sorry for the confusion with the components. My Accumulator used to find itself a nice thick layer of frost, and no longer does. There is a little bit of crud in the fins of the condenser, but not a whole lot. I'll drive to a nearby car wash and wash it off (after it sits for a few).

-I'm aware that one can blow one's hand off, and that blindly adding refrigerant is not smart - both because they will get you nowhere. That's why I want the gauge.

-Mr Benstein, nope I'm only a wee college lad, but I appreciate the sentiment. I had a few other cars I recharged A/C on. In those cases, it was R134 and easy as pie. They were low and I refilled them to factory spec.

-I find the warnings about AC service (and many other things) are a bit like the HUGE warnings that there are no serviceable components inside a piece of small electronics. Bah. Soon they will be on our hoods. Enough knowledge to respect high pressures is enough to make me cautious, and enough to keep me safe.

-If I use a side-can tap, it punctures the thin wall of the can, and I could tap a can of spray paint just as well as cans of refrigerant.

-I found an R-12 can tap at autozone last night, but it had no gauge.

It doesn't seem like anyone has a "hey I got one at harbor freight for $5" solution, so I'll keep searching as a pet project until next summer. Unless it's 90 in january again. :D


Thanks everybody,
Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond

First of all I usually do not hang out on the 700 series.

Your title caught my eye. Then, your casual way of treating A/C in the posting. All is causing me some concern and worry.

I have only 240's and a'91 which is similar to yours. The thing you described as frosting should be the accumulator. It is located at the firewall.

A drier is on the condenser located in front of the radiator. If it is frosting you have a restriction inside it and that would not be good.

Your system probably doesn't have asight glass mounted on top of the drier. If it did we wouldn't be having the chat. You could just fill it up.

Because your system has a different expansion device that was removed and the accumulator is used. This is because the expansion device is a fixed output device.

The system is balanced charged by weight of liquid refrigerant. So much is on each side of the expansion device at any given time or the compressor shuts off to keep from too much being pulled back to the compressor. The reason for the accumulator. Then again too much put into the condenser can happen if both sides are too full. Then your talking too much of everything.

Do you get the picture?

There are more things involved than just pressure difference. Quantity! Like having two buckets full of water and no way to pour them back and forth. Case of more is not better!

You can charge this system without gauge sets. It foolish not to use them because their handy.

It can be done with just a fine scale that weighs in ounces i.e. postal and a thermometer. I use a 70 lb. one from Harbor Freight (because I use large bottles) that I got on sale for about $35.00 (normal $59.00) With it I don't need a thermometer!

If you forget that expensive notion. Then the cheap route then...shade tree it

Evacuate all other gases! Add only one type of refrigerant. Watch until the accumulator sweats and the suction hose feels cold. The outlet temp at the center outlet is about 57 degrees. The condenser should be hotter at the top to about half way down to just warm to the bottom.

You just don't want to over fill it or the efficiency goes into the toilet!

Talking about efficiency. Switching to 134a or other replacements for R-12 you lose about 10%. Like going from clean water in your buckets to some muddy stuff.

Be careful with all your make shift connections. You don't need frost bit fingers or that glazed over look in the eyes in mid summer. Its just plain hard time to try to lie about what happened!

Phil

Is the push fan working good? It should come on at idle after a short time. You should feel it come on at red lights and other stops along the way.

Be sure to evacuate the air from the line between the can and the low pressure valve. Air has moisture in it and will freeze in the expantion tube causing poor performance.
Bob

Thanks for the input - Yes, the aux fan is working full speed. I don't feel a lot of air coming out through the radiator, but I trust it's going through the condenser. There is the condenser, extra trans cooler, intercooler, and radiator for the air to pass through.

Also, I don't think it's an airflow issue because the condenser fins are about 90% clean and the AC doesn't do any better at freeway speeds or idling in my driveway with the fan switched on. I will sometimes stick my pocket knife in between the contacts on the radiator switch (don't touch the knife and the car at the same time!) to force the fan to come on.


happy bricking
-Will
--
1990 740 Turbo, on its way to stock specs, maybe beyond