The right ac gas pressure?

[Rubba]

Hi everyone,
I had a leak in the ac gas pipe last week, i have fixed and refilled it with R134a.
I read that i have to fill it with 500g but the problem is i dont know how much is that in "psi"
So if anybody have any info or can check his car pressure and help me out.
Thanks a lot.

[diagnosticator]

From the evacuated state of the system, that is with the system pumped down to a full vacuum, with no air or refrigerant in the system, A container of R134A refrigerant is placed on a scale measuring weight in grams mass. The bottle is connected to the low and high side access ports using an HVAC Gauge Manifold, and the valves on the manifold are opened to allow refrigerant to flow into the system low side fill port. With the system filling from the bottle, the weight of the bottle is noted before filling is started, and after 500 grams of R134A (plus 5 oz of PAG compressor oil,) are added to the A/C system, ( the bottle being 500 grams lighter weight compared to the begining bottle weight in grams.) the valves are closed on the manifold set. and the hoses are disconnected from the service port fittings on the HVAC system. Done.

[Rubba]

From the evacuated state of the system, that is with the system pumped down to a full vacuum, with no air or refrigerant in the system, A container of R134A refrigerant is placed on a scale measuring weight in grams mass. The bottle is connected to the low and high side access ports using an HVAC Gauge Manifold, and the valves on the manifold are opened to allow refrigerant to flow into the system low side fill port. With the system filling from the bottle, the weight of the bottle is noted before filling is started, and after 500 grams of R134A (plus 5 oz of PAG compressor oil,) are added to the A/C system, ( the bottle being 500 grams lighter weight compared to the begining bottle weight in grams.) the valves are closed on the manifold set. and the hoses are disconnected from the service port fittings on the HVAC system. Done.

Thanks for your reply, but what happened is the ac after refilling was filled with a 1000g the values didn't close or do anything, and the ac was not working properly, so today i removed some gas and keep it at 45 psi.
It worked better than it was but i dont know what to do :/

[diagnosticator]

Thanks for your reply, but what happened is the ac after refilling was filled with a 1000g the values didn't close or do anything, and the ac was not working properly, so today i removed some gas and keep it at 45 psi.
It worked better than it was but i dont know what to do :/

System pressure cannot be used to determine how much refrigerant is in the A/C system. This is because the pressure in the A/C system with the A/C not operating, and at the ambient outside air temperature, varies directly with the temperature of the A/C system at ambient outside air temperatures. The system pressure does not vary according to how much refrigerant in in the system.

In fact, using a temperature vs pressure chart for R134A, you can determine the system temperature by measuring the system pressure with the system OFF and at the same temp as the outside ambient air

In order to fix this problem with the wrong amount of refrigerant in the system, the R134A must be removed from the system and stored, then the system must be evacuated down to a full vacuum, then the correct amount of R134 A is added back into the A/C system by measuring the begining weight of the R134A supply bottle, then stopping filling when the bottle is 500 grams lighter weight compared to the begining bottle weight.

[imnuts]

For a given ambient temperature, the vapor pressure will be constant. That is why you should follow the procedure outlined by diagnosticator. It is quite simple to over charge the system, so I'd recommend that you take it to a qualified shop to get evacuated and refilled.

Sent from my DROID Turbo 2

[imnuts]

Pressure can only be used to determine 2 things for an AC system. If the system is undercharged, with no liquid in the system, the pressure will be low. You could also tell if something is in the system besides R134a and oil if pressure is too high. In an uncontaminated system, pressure will remain constant as soon as liquid forms until there is only liquid in the system and no gas at all.

Sent from my DROID Turbo 2

[diagnosticator]

For a given ambient temperature, the vapor pressure will be constant. That is why you should follow the procedure outlined by diagnosticator. It is quite simple to over charge the system, so I'd recommend that you take it to a qualified shop to get evacuated and refilled.

Sent from my DROID Turbo 2

Thanks for adding that, I agree.

[Rubba]

System pressure cannot be used to determine how much refrigerant is in the A/C system. This is because the pressure in the A/C system with the A/C not operating, and at the ambient outside air temperature, varies directly with the temperature of the A/C system at ambient outside air temperatures. The system pressure does not vary according to how much refrigerant in in the system.

In fact, using a temperature vs pressure chart for R134A, you can determine the system temperature by measuring the system pressure with the system OFF and at the same temp as the outside ambient air

In order to fix this problem with the wrong amount of refrigerant in the system, the R134A must be removed from the system and stored, then the system must be evacuated down to a full vacuum, then the correct amount of R134 A is added back into the A/C system by measuring the begining weight of the R134A supply bottle, then stopping filling when the bottle is 500 grams lighter weight compared to the begining bottle weight.

For a given ambient temperature, the vapor pressure will be constant. That is why you should follow the procedure outlined by diagnosticator. It is quite simple to over charge the system, so I'd recommend that you take it to a qualified shop to get evacuated and refilled.

Sent from my DROID Turbo 2

Pressure can only be used to determine 2 things for an AC system. If the system is undercharged, with no liquid in the system, the pressure will be low. You could also tell if something is in the system besides R134a and oil if pressure is too high. In an uncontaminated system, pressure will remain constant as soon as liquid forms until there is only liquid in the system and no gas at all.

Sent from my DROID Turbo 2

Thank for the info Will keep that in mind
Learnt some new stuff today.

[Seerlah]

Using the PT chart you want a 40 degree coil (low side pressure) for ac systems. Condensing (high side) pressure using a PT chart should be anywhere from 5-25 degrees higher than ambient temp, depending on condenser efficiency (seer rating). Most just cut the calculations required for charging to "proper" condensing temps and stick with 10-15 degree above ambient temp. Just makes things easier.