How much charge the A/C ??

[chorrillano]

Hello

Somebody knows how much PSI should have the A/C when is full charged, I'm thinking to recharge but first I plan to mesure how much pressure in PSI is right now before try lo recharge, so only if it´s low I´d recharge the system

Am I asking nonsense?

Also, is there any difference between R134 and R134a gas?

[sx4mouse]

I (and many others) have had horrible experience charging the A/C from a can. I highly recommend you take it to a pro.
There are threads on this forum about our bad experiences.

See:
http://clubsx4.com/forum/showthread.php?t=6387
http://clubsx4.com/forum/showthread....2399#post92399

[chorrillano]

I see, thanks

I´ll take the car to a shop, but I want to know the right pressure anyway, to be informed and they cannot lie to me.

[Schultzey]

The expected high and low pressure ranges according to ambient temperature can be found in the factory service manual (FSM). There are FSMs available on the forum for 07-09 SX4s at http://clubsx4.com/forum/showthread.php?t=5. The one you reference will be dependent on the vehicle type you have. It may be helpful to use your VIN to confirm you are using the right manual.

Here are a couple examples:

• If you have an SX4 with a 2.0L engine confirm it matches the "Applicable Model" criteria of "SX4 (RW420) produced at KOSAI plant in Japan with following vehicle identification number (VIN): JSAGY############ ~ or JS2Y#############~". If this matches download the RW420 FSM and look on page 7B-9 to see the graph of acceptable pressure ranges on the high and low pressure ports according to the ambient temperature.

• If you have an SX4 with a 1.5L or 1.6L engine confirm it matches the "Applicable Model" criteria of "SX4 (RW415/RW416) produced at KOSAI plant in Japan with following vehicle identification number (VIN) JSAGY############ ~ or JS2Y#############~". If this matches download the RW415/RW416 FSM and look on page 7B-9 to see the graph of acceptable pressure ranges on the high and low pressure ports according to the ambient temperature.

Even though both FSMs have the pressure graph on the same pages the acceptable pressure ranges are slightly different. This is why it is important to reference the correct manual for your vehicle.

There is a difference between R134 and R134a. While they both have the same amount of atoms the arrangement is different. R134 is less effective at moving heat. Suzuki specifies that you only use R134a.

[LMP]

A/C pressure (system at rest) is a function of temperature, period, whatever the quantity, in as much as there is enough refrigerant so that it exists in both the liquid and vapour phase. This is a law of thermodynamics and the refrigerant exists in the system as partly liquid and partly vapour and in this condition , whatever the proportion, the pressure is always the same for a given temperature and known as "vapour pressure".
see here
http://www.csgnetwork.com/r134apresstempconv.html


Vapor pressure (at 5 °C or 41 °F) : 3.5 bar
Vapor pressure (at 15 °C or 59 °F) : 4.9 bar
Vapor pressure (at 20 °C or 68 °F) : 5.7 bar
Vapor pressure (at 50 °C or 122 °F) : 13.2 bar

bar is absolute ..so for gauge pressure substract 1 to figures above....5.7 absolute is 4.7 gauge...
4.7 bar gauge = 4.7 x 14.7 psig = 69 psi(gauge)

Remember: this is true only if you have SOME of R134 in liquid form.
If at a given temperature the pressure is less than the table, it means you have NONE left in liquid state...which means, practically speaking, that you have virtually none left, the vapour phase occupying a lot of volume for a very small actual quantity.

At that point, you must simply feed in the QUANTITY that is specified for that system...regardless of the pressure that will be obtained during that process, which can vary a lot if the engine is running the A/C pump and all of this in a varying temperature environment.

The charge in the SX4 shop manual is 430 +/- 20 grams....or 15 +/- 1 ounce (by weight)..hence about 13 liquid ounces (density is 1.2)

I use to do this without running the engine, system cold , and simply having the refrigerant can in a bowl of slightly warm water, like 100°F, ...the can at a higher temperature than the system will be at a higher pressure hence it will flow in effortlessly.

www.avigex.ca/sx4/ACcharge.pdf

[chorrillano]

Great ... Thank you

[Dr. No]

Another great example of "use the search". Fantastic information here. (Yeah I know it's old...)

[LMP]

By the way, after 10 years, the A/C proved inoperative for lack of refrigerant. There was still some pressure in the system, but less than vapor pressure, meaning none was left in liquid phase. . I bought a 12oz can of R134A, (on line from WalMart Canada) hooked it to the system low pressure port, engine inoperative and cold, heated the can (so it was at a higher pressure than the system) with a 60watt light bulb kept a few inches away; all the R134 was delivered.
A/C working fine now.
IN Canada, Canadian Tire sells Red12... which is propane gas; the can is labelled as "contents highly flammable"....it works indeed as a refrigerant; I hate this ; never mix with R134A.