checking air conditioning pressure in a '94 Tercel fixes A/C without adding refrigerant

Hello
I have a '94 Tercel as my second, city car. The A/C has been running barely cool at the max setting, taking 15 minutes maybe to even get to sorta cool. Last time I had the
A/C looked at was back in 2001, when I had it converted over to R134 refrigerant and fully charged with it. So I bought a bottle of the stuff, one with a built-in pressure gauge. The first reading I got was just above 20 pounds--about 5lb out of spec I think. Then, without me adding more refrigerant, the pressure started to rise, up to about 32-33lbs. So I get back in, and the air is mucho colder.
So, what exactly could I have done to fix it? The R134 bottle I got has a button you have to press down (rather firmly) to release anything, and I didn't press it at all. Could just checking the pressure have stirred up some refrigerant that had "settled" or something...though I guess that doesn't make sense since gas doesn't really settle.
As you might guess I know relatively little about auto aire conditioners; doing something like this is about my limit as far as repairs on 'em can go.
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That is a bit odd. My sister's 94 and 95 Corollas both came with R-134. My 93 came with R-12.
Charles of Kankakee
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On Mon, 04 Jul 2005 07:06:27 +0000, Ryan Meier wrote:

Interesting. Let us know if it stays cold!
My un-educated guess is there was perhaps some sort of blockage that you dislodged by connecting the bottle, or the system was a bit overpressurized and you released some by connecting the bottle. At any rate, you dodged a pretty big bullet by trying to fix it yourself.
Or, there was moisture in the system that dissapated when you opened the valve.
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What do you mean? As in, it's dangerous to fix somethling like this, or I could have easiyl runied smething? Just wondering...

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wrote:

If you over-pressurize the system, you can damage the compressor or seals in the system or worse, the can could burst on you (which is why the are known to automotive pros as suicide cans).
If the pressure when from 20 psi to 32 or 33 psi, then you probably added refrigerant to the system without knowing it.
Next time you get insufficient cooling, start the engine, turn on the AC, and open the hood. In front of the radiator and condenser will be the receiver/drier. It is a canister about the size and shape of an aerosol can, with a line going in and out of the top and a round glass window, known as a sight glass. With the AC operating and refrigerant at proper levels, you should barely be able to see anything going on in the sight glass. If you see white foam streaming past, then refrigerant levels are too low and air is in the system. It is normal to gradually lose refrigerant (R-12 freon or R-134A) over time, and the less you use the AC, the quicker it happens because the oil that is in the system doesn't get circulated.
Just adding refrigerant with those suicide cans is not the proper way to service the AC system. Besides the refrigerant, there is a spec for the proper amount of special refrigerant oil. To properly charge the AC system, a vacuum pump and AC refrigerant recycling machine and gauges should be attached, the system evacuated, and then the coolant and lubricating oil put back in.
I do most of my own work on our cars but since I don't have a vacuum pump and means to capture the refrigerant, I bring it in to a shop for proper service.
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"Ray O" wrote:

I guess you have not "gaged" many systems then because 30 PSI is not high for a Toyota that has been converted. It should be between 30 and 40 PSI on low side on a hot day and even blower speed can effect low side pressure so it is wrong to assume his pressure is bad.
"Ray O" wrote:

So do I and have for over 27 years with A/Cs. A freind taught me the "ropes" long ago on it and I have done my own work every since for automotive to central air systems and I have a pump too. I have never had a A/C system serviced by someone else on a car or a home that was not under warranty. If you know the ropes, you know how varible the pressures can be as tempature and humidity changes. With practice you can tell when a system is properly charged and in good health just by reading the high and low side pressures relative to tempature and humidity. Also you will have higher pressures than it did when R12 was in the system by 10 to 15% as well.
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I didn't say that 30 PSI is too high or bad. I said that if the pressure was 20 PSI before the OP hooked up the suicide can and 32 to 35 PSI afterwards, then the OP probably released some R134A into the system.

As a former District Service Manager for Toyota Motor Distributors with ASE Master Tech status, I have some knowledge of AC systems. I have only had one vehicle that needed a refrigerant charge in 30 years, so I didn't think it was worth it for me to invest in a pump and refrigerant recovery system. Since it is illegal and irresponsible to discharge refrigerant into the atmosphere, how do you recover the refrigerant when you evacuate the systems you work on?
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On Mon, 4 Jul 2005 14:15:51 -0500, "Ray O"

Good luck on most cars running R-134a, they've stopped installing sight glasses on most of them. Saves them maybe 50 cents per car, and when you sell a million cars or more a year that adds up...
You need a $200 gadget known as an "electronic sight glass" that clamps onto the high pressure hard line and by detecting them with ultrasound "shows" you the bubbles going by (or not) on a display.
I gotta go get me one of those...

The oil charge in the refrigeration system /usually/ does not leak out of the system in quantities significant enough to affect anything in your normal "every 5 years" leaks, unless your little leak happens to be at the very bottom of a connection point. And when they track down the refrigerant leak, there probably will be signs of an oil leak from that spot, too - a big schmear of oil-captured dirt running down the hose, or on the frame rail below it.
But if you take the AC compressor out to install a new or rebuilt unit, or a car accident or a hose blowing off causes a zero-leak, that's when you have to drain and refill the compressor oil charge to make sure you have enough oil in there.

Which is the prudent way to do it. ;-)
--<< Bruce >>--
--
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Electrician for Westend Electric - CA726700
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"" wrote: > On Mon, 4 Jul 2005 14:15:51 -0500, "Ray O"
> > >Next time you get insufficient cooling, start the engine, > turn on the AC, > >and open the hood. In front of the radiator and condenser > will be the > >receiver/drier. It is a canister about the size and shape of > an aerosol > >can, with a line going in and out of the top and a round > glass window, known > >as a sight glass. With the AC operating and refrigerant at > proper levels, > >you should barely be able to see anything going on in the > sight glass. If > >you see white foam streaming past, then refrigerant levels > are too low and > >air is in the system. It is normal to gradually lose > refrigerant (R-12 > >freon or R-134A) over time, and the less you use the AC, the > quicker it > >happens because the oil that is in the system doesn't get > circulated. > > Good luck on most cars running R-134a, they've stopped > installing > sight glasses on most of them. Saves them maybe 50 cents per > car, and > when you sell a million cars or more a year that adds up... > > You need a $200 gadget known as an "electronic sight glass" > that > clamps onto the high pressure hard line and by detecting them > with > ultrasound "shows" you the bubbles going by (or not) on a > display. > > I gotta go get me one of those... > > >Just adding refrigerant with those suicide cans is not the > proper way to > >service the AC system. Besides the refrigerant, there is a > spec for the > >proper amount of special refrigerant oil. To properly charge > the AC system, > >a vacuum pump and AC refrigerant recycling machine and gauges > should be > >attached, the system evacuated, and then the coolant and > lubricating oil put > >back in. > > The oil charge in the refrigeration system /usually/ does > not leak > out of the system in quantities significant enough to affect > anything > in your normal "every 5 years" leaks, unless your little leak > happens > to be at the very bottom of a connection point. And when they > track > down the refrigerant leak, there probably will be signs of an > oil leak > from that spot, too - a big schmear of oil-captured dirt > running down > the hose, or on the frame rail below it. > > But if you take the AC compressor out to install a new or > rebuilt > unit, or a car accident or a hose blowing off causes a > zero-leak, > that's when you have to drain and refill the compressor oil > charge to > make sure you have enough oil in there. > > >I do most of my own work on our cars but since I don't have a > vacuum pump > >and means to capture the refrigerant, I bring it in to a shop > for proper > >service. > > Which is the prudent way to do it. ;-) > > --<< Bruce >>-- > > -- > Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop > Electrician for Westend Electric - CA726700 > 5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545 > Spamtrapped address: Remove the python and the invalid, and > use a net.
A typical car A/C system has about 6 to 8 oz of oil in it total but usually there is no more than a few ozs at a time that stays in the compressor.
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On Mon, 04 Jul 2005 18:59:40 +0000, Ryan Meier wrote:

Well, as SnoMan says, 20 PSI was low, so adding a bit helped. What I was talking about was compressor/condensor/receiver-drier type stuff. Condensor is about $265, condensor is about $110 and a receiver-drier is about $150. So, your $14 can of R-134a saved you quite a bit (and most places are charging about $100 to charge a system!)

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"hachiroku" wrote:

it.
got
any
No mystery here at all. It is likely under charged a bit and the low pressure swith is kicking in from time to time and limiting cooling
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"" wrote: > Hello > > I have a '94 Tercel as my second, city car. The A/C has been > running barely cool at the max > setting, taking 15 minutes maybe to even get to sorta cool. > Last time I had the A/C looked at was > back in 2001, when I had it converted over to R134 refrigerant > and fully charged with it. > So I bought a bottle of the stuff, one with a built-in > pressure gauge. The first reading I got was > just above 20 pounds--about 5lb out of spec I think. Then, > without me adding more refrigerant, > the pressure started to rise, up to about 32-33lbs. So I get > back in, and the air is mucho colder. > > So, what exactly could I have done to fix it? The R134 bottle > I got has a button you have to > press down (rather firmly) to release anything, and I didn't > press it at all. Could just checking > the pressure have stirred up some refrigerant that had > "settled" or something...though I guess > that doesn't make sense since gas doesn't really settle. > > As you might guess I know relatively little about auto aire > conditioners; doing something like this > is about my limit as far as repairs on 'em can go.
The pressure in the low side (which your gage reads) is very dependant on the tempature and humidity of the air it is cooling. (the hotter and more humid it is, to higher the pressure. If I had to give you the "norma" on a hot day it should be between 30 and 40 PSI. 20 PSI is low unless it is cool outside. It sounds like you might be a little low and the low pressure switch it restricting cooling sometimes.
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