has anyone used these 134a top up cylinders? I checked the a/c pressure and topped it up to just in the green = to 30psi it had been on 25psi. what is the best pressure for 134a and sanden compressor, it is cold but maybe could be colder. advice please

 

 

Pressures are not really car specific, it's a pressure vs. ambient temperature factor you need to correct for.





And throw away those store cans, the gauges are not reliable in any sense of the word. You need a set of manifolds and a good thermometer.

 

When I can't charge by weight, or using a refrigerant the system wasn't designed for here is my procedure:


Start charging until the compressor engages. Keep adding refrigerant slowly while spraying the condensor with a garden hose to remove the heat. Have the system set to full cold and fans on high. Watch the vent temperatures, they will fall as you add refrigerant and at some point the compressor should switch from running continuously to cycling.


At some point the vent temps will reach a minimum and then start to slightly increase. This is the point when it's fully charged. Both low and high side pressures will increase rapidly with additional refrigerant at this point, prior to this the pressure shouldn;t move much when adding refrigerant. With effective heat removal by the hose, you should be able to get vent temps down to the 3-4 degree range if everything else is in top shape. There is a thermal switch that should turn the compressor off when the evaporator core reaches just above zero, as you don't want the air to freeze.


As you are charging, also feel the pipes that run on the left side of the engine bay. This is the return to the compressor. It should be cool, but not cold. If it's cold and frosting that probably means it's over charged and you have refrigerant carry over from the evaporator. You don't want this, as liquids are incompressible and will damage the compressor.


The idea is when fully charged the evaporator core inside the car is full of boiling refrigerant, but not more, you don't want liquid to pass through the evaporator. The hot air inside the car should be able to completely boil all the refrigerant, so only vapour is returning to the compressor, by way of the fuel cooler.


I also have gauges hooked up to the system and keep an eye on the pressures. For my ambients I'm typically looking around 30-35psi on the low side, but I rely more on the vent temperatures. pressures will go up with temperature, that's why I use the hose to make sure I have very efficient heat removal. Without that the pressure will increase when driving and in standing traffic.


AC charging is a bit of an art, and part science.

 

Opps doubled my reply and can't delete one?

 

Jagbio64; That's one of the best explanations and procedures I've ever read for charging an AC system...good job

 

Dose anyone have a pic of the location of the low press inlet or side. I am probably staring right at it but can't seem to find it.


TIA
David