A/C System R134a

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Yesterday was 94F here and I noticed A/C system on 04 Camry was not cooling as in summers past. Compressor is engaging and low pressure line is somewhat cool to touch but not cold and sweaty. I usually have an A/C thermometer stuck in the middle discharge vent but haven't got around to installing it yet so I don't know what discharge air temp was NOT cold enough for sure for my wife. All fans functioning normally. Local Toyota dealer and another shop want to completely evacuate system/dehydrate and then refill R134a as measured on a digital scale. Something about EPA regs. My question is: are the A/C refill kits accurate enough to just add refrigerant? I have the gauge and hose setup from a kit I purchased years ago. I'm considering purchasing a can of R134a without sealer and adding enough to get the gauge reading in the green.I realize that A/C service is best left to trained techs, but vehicle is on 18th summer cooling season and I'm weighing cost of purchasing a new vehicle. My war department is very,very much bothered by hot weather and I don't want the #@&^%$@$^ about a hot car. Advice appreciated.
 
The purpose of doing an evacuation and refill is to know precisely how much refrigerant is in the system. If you just dump a can of refrigerant into the system then you have no idea of what you have.

If your system has never been topped off in 18 years then you're low. Even though they say they are closed systems,, everything leaks a little bit over time. I'd just put a 12 oz can into the low pressure port and see how it goes.
 
Bring it in the the shop and have it leak tested then the evac and recharge if good. a new car is a great idea . If you want to milk the car yes add some gas with leak stop.
 
Originally Posted By: FowVay
The purpose of doing an evacuation and refill is to know precisely how much refrigerant is in the system. If you just dump a can of refrigerant into the system then you have no idea of what you have.

If your system has never been topped off in 18 years then you're low. Even though they say they are closed systems,, everything leaks a little bit over time. I'd just put a 12 oz can into the low pressure port and see how it goes.
The evac removes the moisture from the system.water boils in a vacuum.
 
If you're going to add, at least get a gauge with some kind of temperature correction for the "green" zone. It's easy to overcharge if you just dump a can in there. Although I used the A/C Pro successfully on a car I wasn't planning on keeping, word on the street is the shops really hate that stuff because the stop-leak fouls up their machines.

Tip: Get a bucket of hot water to dunk the can in as you're adding, it will get cold and you may not be able to get it all out without some help.
 
Sounds like you might just need a top off. The chintzy gauges that come with those kits aren't the best but you've just got to add refrigerant slowly. I added about half a can of pure R134a (none of that stop leak [censored]) to my Accord a couple of summers ago. It was a 90 deg day and I only charged up to 32 PSI. The temp & pressure chart they provide is on the higher side, IMO. A/C's been working great ever since. I can tell the charge is good since the compressor doesn't cycle too much.
 
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Originally Posted By: CT8
Originally Posted By: FowVay
The purpose of doing an evacuation and refill is to know precisely how much refrigerant is in the system. If you just dump a can of refrigerant into the system then you have no idea of what you have.

If your system has never been topped off in 18 years then you're low. Even though they say they are closed systems,, everything leaks a little bit over time. I'd just put a 12 oz can into the low pressure port and see how it goes.
The evac removes the moisture from the system.water boils in a vacuum.
Thanks. I understand the fundamentals of dehydrating a refrigeration system from a seminar put on by Robinair (?) at our power generation station decades ago. We had many A/C systems for our various control rooms, training and admit buildings.I remember Robinair was trying to sell the company several two-stage vacuum pump carts. They were nice units and being on wheels they both rolled right off the plant site never to be seen again.
 
Originally Posted By: FowVay


I'd just put a 12 oz can into the low pressure port and see how it goes.
No way! Terrible advice! His camry only holds 19oz total! It may only be 3-4oz low. Adding 12oz will be a huge overcharge.
 
Still have R12 in my 83 Silverado, Ice Cold.
cheers3.gif

Had the AC system reworked 2 yrs ago.
 
Originally Posted By: Chris142
Originally Posted By: FowVay


I'd just put a 12 oz can into the low pressure port and see how it goes.
No way! Terrible advice! His camry only holds 19oz total! It may only be 3-4oz low. Adding 12oz will be a huge overcharge.
Right you are Chris. My OEM shop manual shows system holds 19.37 ozs, plus/minus 1.76 ozs. Somewhere between 18 and 21 ounces. That's the problem I have with adding refrigerant since the range between low and overfilled is only about three ounces. Depending on how accurate my old gauge set up is, I could easily put too much 134 in the system. Got to do something soon as temps in nineties approaching 100 are continuing.Thanks
 
I would recharge with a can and a gauge. These cans don't empty all at once, unless you fully open the valve.
I always purge the line, hook up the gauge, close the valve on the can and let the pressure settle before adding anything. When it comes to adding, I would open the valve just enough to see the pressure rise on the gauge about 10psi, add for few seconds, close the valve and see the new pressure reading. Repeat until pressure looks good and the line is nice and cold.
 
Sometimes mechanics want to evacuate your system so they can tell you that your system leaks and it will be illegal for them to put YOUR refrigerant back into your system, then they sell you a compressor, evaporator, drier etc. That is basically how most operate in San Diego, one big rip off industry here.

I agree with above, just add slowly until it's working again...and stop there, don't give it a little extra.
 
I was in a similar situation a couple years ago with my '99 Mazda. I didn't want to put much time or money into a car that old. Many cars that are over 15 years old have leaked enough refrigerant that the AC system does not work so well.

I just bought a manifold set and a thermometer. I watched both the gauges and the thermometer that was stuck in the center vent and added 134a until I got acceptable readings.

That was 2 years ago and it has been working good since.
 
Originally Posted By: another Todd
That is basically how most operate in San Diego, one big rip off industry here.


And there's always the drive to Tijuana to get it worked on cheaply as well.
smile.gif


Newer AC systems are sensitive to oil fill and refrigerant charge, the tolerances for oil fill are +/- 5cc and +/-10-50g for refrigerant.

There will always be small losses through the hoses.
 
Originally Posted By: CT8
Originally Posted By: FowVay
The purpose of doing an evacuation and refill is to know precisely how much refrigerant is in the system. If you just dump a can of refrigerant into the system then you have no idea of what you have.

If your system has never been topped off in 18 years then you're low. Even though they say they are closed systems,, everything leaks a little bit over time. I'd just put a 12 oz can into the low pressure port and see how it goes.
The evac removes the moisture from the system.water boils in a vacuum.

Yes, the evac removes moisture from the system, but the main reason for removing all the refrigerant and refilling is so you know exactly how much refrigerant you have, as FowVay said. Moisture isn't really an issue in a system that still has refrigerant and is still at least somewhat working. It's only really an issue if you've opened the system up to replace a component(s) and humid ambient air got in the system. Once you have the components replaced, you vacuum it to remove the air from the system as well as the moisture, and then you're ready to recharge.
 
Originally Posted By: exranger06
Originally Posted By: CT8
Originally Posted By: FowVay
The purpose of doing an evacuation and refill is to know precisely how much refrigerant is in the system. If you just dump a can of refrigerant into the system then you have no idea of what you have.

If your system has never been topped off in 18 years then you're low. Even though they say they are closed systems,, everything leaks a little bit over time. I'd just put a 12 oz can into the low pressure port and see how it goes.
The evac removes the moisture from the system.water boils in a vacuum.

Yes, the evac removes moisture from the system, but the main reason for removing all the refrigerant and refilling is so you know exactly how much refrigerant you have, as FowVay said. Moisture isn't really an issue in a system that still has refrigerant and is still at least somewhat working. It's only really an issue if you've opened the system up to replace a component(s) and humid ambient air got in the system. Once you have the components replaced, you vacuum it to remove the air from the system as well as the moisture, and then you're ready to recharge.
Right you are ex, pull a system down to around fifty microns and moisture in a system will boil at something like -50F.I remember that the two Robinair two-stage vacuum pumps we had before they walked off the plant site would pull down to 50 microns.And after thirty some years I still have a very good idea of who took those machines.
 
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