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How to add freon


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I got the "Low Refrigerant" warning on the CRT, and it seemed to set a B446 code.

To my surprise, it looks like the car WAS converted to 134a, because the port on the accumulator looked like the new style. It had internal threads, and a plastic cap on it.

Anyone have tips/instructions on how to add freon? Where is the port located, to hook-up the can? Etc. etc.

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If you system has been converted, the connectors will not have external threads, internal threads are for the Schrader valve.

134 hose connector has a quick disconnect, not a screw on fitting.

You add to the LOW side of the system....... that would be at the silver cylinder, down low behind the radiator.

You can purchase 134A several ways. If you do not have gages, then I would recommend buying a refill can that has the gage.

Use caution because you can add too much refrigerant. I also suggest you do a search for "134A cooling chart" the chart will give you recommended pressure for the outside temp at the time you are working on the system.

The pressure on the gage is used to determine the cooling temp. It is a little more complicated than that but on a 80 degree day, the gage should read 45-50 psi. Take a reading before opening the valve on the can, most likely you will have a high reading....above 60.

When you open the valve, refrigerant will go into the system, the added refrigerant will disrupt the internal pressure and the gage is between the car and the incoming refrigerant, so the gage will give you a false reading........turn off the valve and take a reading, it should be dropping.

Also, depending on the outside temp, it will take longer the hotter it is outside.

So add some, turn off the valve and take a reading, if still high, add some, turn off the valve and take a reading..etc, etc

Edited by Barney Eaton (see edit history)
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  • Roll the windows down or open the doors.
  • Set the climate controls to AUTO.
  • Be sure you have the temperature control set to MAX-cool.
  • Place a box fan in front of the radiator. (If you have one.)
  • Connect the filler hose to the LOW SIDE port on the accumulator before starting the car.
  • Hold the engine at 1500-2000 RPM when adding freon.

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Thanks for the tips!

Yes, the fitting on the accumulator looks just like a "shop air" quick disconnect, with NO external threads. It does have internal threads, which is what the plastic cap picks-up when screwing that on. So, it sure looks like it was converted.

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Temp vs Pressure Chart - 134a - AC Auto Repair Help Forum

This chart computes gage pressure into refrigerant temp. Note that 28-29 psi is very close to freezing and you do not want to ice the evaporator. What the chart does not show is the changes as outside temperature goes up and down.

R-134a System Pressure Chart - IDQ USA

This chart shows pressure and how it changes with outside temperature.

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Ok, I need help.

I hooked up the refill container (that has a gauge), and it read 0 psi. My code also was now B447 (was B446). So, I turned on AC and started adding. The compressor was clicking on and off every second, and when it did that, the engine rpm's would race up to 1200 and then back to 800. While the compressor clicks on and off, the gauge would go from 0 psi to around 25 psi (basically in the white zone, below the green zone) while I wasn't filling. I continued to add, and the compressor still clicked on and off. I had to keep clearing the BCM codes, to turn the AC on again. When the compressor stopped clicking, the gauge slowly crept into the red zone. I hope I didn't over fill it, so I bled a little out.

Then, I cleared the code, and tuned AC on, and watched the gauge. The gauge rises and falls within the white zone with the compressor coming on and off, and when the cycling stops, the gauge now creeps into the middle of the green zone.

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What type of help are you needing?

The pressure reading will be low when the compressor is running and high when it is disengaged.

Keep in mind that you have the gauge connected to the 'suction' side of the compressor. So... when the compressor engages the pressure will start to drop until one of several things happen to cause it to disengage. Such as:

-The pressure drops so low that the Low Pressure Switch will send a signal to the BCM causing it to disengage. (Sometimes locking the compressor out until it is reset to protect the compressor.)

-The Low Temperature Sensor will send a signal to the BCM telling it the evaporator is getting cold enough to freeze up. (The compressor will be disengaged until the evaporator temp comes up to normal operating temperature.)

There are a lot more conditions that come into play but this gives you an idea about what is going on. Normally some cycling of the compressor will take place depending on a number of factors like climate control temperature settings, cabin temperature, outside temperature, etc.

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Thanks for the info.

Update: So far, I added an entire 20 oz can, which got me just into the "green zone". Then, I added a 12 oz can that brought me up to approx 1/3 into the green zone (i.e. approx 35 psi). I then proceeded to add another 12 oz can, which really didn't seem to raise the pressure much more than the previous 12 oz can. So, being that it was 80F out, should I have kept adding even more, to try to raise it to 45 psi???

I just didn't want to overfill. The a/c seems to be working fine; I'm just right below the "V" section of the adjustable gauge (when it's set to point to 80F).

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I'm not familiar with the markings you describe on you gauge. Do you have a thermometer you could put inside one of the vents to measure the temperature of the air coming out?

If you are satisfied with the way the the system is cooling the car then you are probably OK with the amount you have in there now. If you suspect you have a leak you might want to stop there and see how long the charge lasts.

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The gauge seems to be the same on all refill canisters that come with a gauge/hose assembly. Here is a pic. The only difference, is my gauge had a white section in lieu of the blue shown in the pic.

I'm thinking I'll hold-off adding more, to see if the system holds the freon........the stuff is very expensive.

The first 20 oz can was regular stuff, and then I figured I should add the stuff with the dye, so the next two 12oz cans had the dye in it.


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You need to know the pressure and forget about the colors.

Here is a link that does some conversion ........ How to Convert R-12 to R-134A | eHow.com

The Reatta takes 2.375 pounds of R12 to completely fill it. (roughly 38 oz)

All the conversion information says that you use between 80 and 90% of that when converting to 134A, lets split that and use 85%.

85% of 38 oz = 32 oz max Looks like you have overcharged the system with 44oz

The cooling curve starts to go back up in temp after you reach the factory recomended "full" amount.

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