@flintknapper can you explain how for a newb charging liquid vs vapor? Is it just a matter of what port youre putting it into or ...?
Yes.
First, lets understand WHEN it is appropriate to 'liquid charge' a system. You NEVER want a liquid charge in the LOW side (it can slug your compressor). The ONLY time I liquid charge...is when there has been a complete evacuation of the system.
Now that we know WHEN we might choose to liquid charge (into vacuum,
engine off) a system, let us understand WHY we do it. The reason(s) to liquid charge the system (initial charge).
1. Liquid charging the first can/12 ozs. into the high side (Into Vacuum) gets 12 ozs. (if using disposable cans) into the system quickly. Typically less than a minute.
2. Liquid charging (into the high side into vacuum) lets you get at least 12 ozs. of refrigerant into the system so that it can carry the compressor oil (lubricant) with it right from start up. You will also have enough pressure to activate the low pressure sensor...so the compressor clutch will operate right away when you go to finish filling the system (via the low side as a vapor).
How do we do this?
Starting from a condition where the system has been pumped down (deep vacuum) to between 28-30 inHg.
All valves closed (valves were closed with vacuum pump still running) to avoid losing any vacuum.
Conditions: ENGINE OFF, System has held vacuum for at least 30 minutes, High and Low side hoses still connected, Yellow charging hose disconnected from pump.
1. Connect yellow hose to can using appropriate adapter. IF using a side piercing adapter, install/pierce near the top or bottom of can (not in the center). We are going to invert the can so the liquid is nearest the piercing point later when we charge.
2. Slowly unscrew the fitting of the yellow hose at the manifold gauge just until a small amount of refrigerant escapes past the threads, then re-tighten. This will purge any air (atmosphere) from that line and prevent any from entering the system. Some hoses have a shrader valve at that location that you can depress to do the same thing. Just be sure to purge the line. Be careful! Just barely crack the fitting to let a little refrigerant out.
3. Invert the refrigerant can so that the liquid refrigerant is nearest the 'tap' (adapter) and keep it in this position.
4. Slowly open the high side valve (until fully open) while making sure the can stays inverted, do not shake, just let the refrigerant be drawn in. You will physically be able to feel the can getting lighter. It shouldn't take too long (typically less than a couple of minutes). The Deep Vacuum will pull the refrigerant into the system. As this process nears its end...the can will become quite cold and the outside might even frost over.
5. Once you are satisfied the can (approx. 12 ozs) has gone into the system,
shut off the high side valve, we won't be using/opening it anymore. Leave the hose hooked up, we still need it for gauge readings later.
6. At this point you are ready to finish filling the system via the LOW SIDE port. There is no more 'vacuum' in the system, we now have a certain amount of pressure (depending upon ambient temp). All future refrigerant will be drawn in as a VAPOR (we don't want liquid, or only very small amounts) going through the compressor. This will be drawn in by the compressor itself and through the LOW SIDE port.
7. So...with High and Low side valves CLOSED, we are ready to connect another can of refrigerant to the yellow hose (with adapter). Connect another can, then just as before....'purge' the yellow line at the manifold connection (just let a little refrigerant escape, then re-tighten it, or use the shrader valve if so equipped).
8. I like to hand turn the compressor 10-15 revolutions (belt(s) off) before installing the belt and running the compressor to insure it turns freely, has no liquid refrigerant in it (that can slug it) and to distribute some of the oil prior to start up. But this extra step is up to you.
9. Now lets start charging the remaining amount of refrigerant (whatever amount your vehicle calls for) as a VAPOR into the low side port. With the refrigerant connected and that line purged, we now need to purge the low side line (blue line). Just slowly crack that fitting (just as you did the yellow line) until a little bit of pressure escapes, then tighten it back up. Now we are ready to go.
10. With your A/C on 'high' and the windows (or doors open), start the engine and your compressor 'should' already be running (clutch engaged). Make sure your refrigerant can has the tap facing UPWARD...so that only gas/vapor will be drawn out. Remember
we don't want liquid refrigerant going through the compressor (at least not your first time, pro's and experienced DIYers know how to 'force' feed it, but DON'T do it for now).
11. Slowly....open the low side valve and allow a small amount of refrigerant to be drawn in. DO NOT fully open the valve, DO NOT shake or invert the can at this point. Just open the valve about a quarter turn and watch your low side gauge. IF the pressure goes above 85-100 psi, turn the valve off for a minute or so and let the system 'settle' or open the valve to a lesser degree. This is going to take some time, so don't rush it. Depending upon the ambient temperature and humidity....it can be difficult to get the remaining charge of refrigerant into the system at times.
12. Continue to charge the system based on WEIGHT of refrigerant, not gauge readings (for a full system recharge). We will use the gauges to fine tune the charge later if need be.
Notes: Go slowly, be sure have turned off all valves before connecting cans of refrigerant and that you PURGE the low side line and refrigerant line each time BEFORE opening any valves to charge the system. Even small amounts of air and moisture will affect the performance of your system.
Make sure you have pulled a deep vacuum on the system (28-30 inHg). This will remove air and moisture. If the system has been open to atmosphere for very long, then plan on pumping it down for a couple of hours or more. It takes time to boil off and extract the moisture.
The point of creating a vacuum (besides removing the air) is to remove the moisture in the system. It has to boil off. The less pressure on the water vapor the lower its boiling point. For instance at approximately 29 inHg. water will boil at about 76° F. So the more vacuum we can maintain, the better.
Moisture in the system can be handled by the desiccant in the drier, if not too much. But if too much...it will migrate to the TXV and Evaporator and freeze up (blocking your system). So let's just do it right the first time.
For best results you need:
1. Properly functioning components
2. A clean system (no contaminants such as air, moisture, stop leak, etc...)
3. Leak free components (compressor, lines, drier, evaporator, condenser). Refrigerant is a NON-Consumable, it can only escape via leaks or be compromised by contaminants.
4. Proper amount of Oil and Refrigerant.
So starting with a new or completely evacuated system is the easiest of all scenarios. We know how much of everything we need, we know (or should know) the condition of everything). It's partially filling or diagnosing a system that is hard. Not this.
